MV8

I'm sure you will figured it out.

Is it 1.25? I would expect 1.75 or 1.5 in aluminum but I don't know.

Y9: MGB 62-80, Midget 61-80. Other PNs: 8G621, QHY9, 282-305 636: A universal type part rather than an oem. Called a "bonded torsion bush". 2030: Same situ. Sometimes double bonded, sometimes peened/crimped around the outer ends. With each replacement, the press fit is a bit easier and could get to be too easy. Knurls on the bush or loctite green retaining compound may be a good idea. Instead of pressing in new, I'd probably heat the old bushes with a hand torch until the rubber popped out, leaving a smooth shell and inner sleeve, then machine nylon or delrin tube inserts and fit uhmw thrust washers. Otherwise, with so many bushes, there isn't much to be saved when a full set is under $150 when bought here.

Ditto. It is just a clamp for the bush inner steel sleeve bonded into the bush and will not move around if the bolt is tight. Had the bolt been a stronger grade (no head marking?) and/or had rolled versus cut threads (a possibility with specialty hardware along with softer material easier/less costly to machine) then you probably would not have a diff out right now. I see no other reason for the bolt failure with such a corrosion-free diff.

It looks like GM #90411542 (PR313) may be a suitable replacement. Compare to what you have as far as fitment and 42-43psi operating pressure.

I think you'd be much better off with a common m12-1.75x85 in 10.9 or 12.9. The oversize shank doesn't make the m12 threads any stronger. It is essentially a shoulder bolt like this: https://www.mcmaster.com/97713A124/ Versus something much stronger like this: https://www.mcmaster.com/91502A253/ The bolt is just a clamp for the inner bush sleeve. No need to be super tight if you have lock washers, serrated step washers, lock tabs or safety wire to prevent loosening. If the threads get damaged, you might consider taping for 1/2 inch instead of a m12 helicoil.

Wrap holds moisture on the surface (less of a problem for garaged, fair weather vehicles) and the insulation raises the temp too high that results in eventual flaking and pipe failure. Wrapping generally voids the warranty on headers. A similar result can occur from only coating the outside of a header but a header that has reasonable wall thickness (16ga or thicker) and is coated inside and out should be able to handle a layer of wrap. A blanket or shield with a riveted on mat over the top where air can still flow underneath should be fine. Many oems do that.

Forgive me for covering anything you already know. If you make a new cover, a same thickness cover or separate starter shim will probably be necessary. If after running, the starter pinion does not release the ring gear, the starter is too deep in the bell. It seems likely the new sump touches the cover only at the lowest point on the pan and it would be hard to tell until you start dimpling. A shallow dimple in the cover would make it fit both pans and be hidden. If you are concerned the cover may spread from the dimpling and no longer fit, the cover could be clamped around the edge to a few strips of bar stock or angle iron before dimpling. You could drill the strips to utilize the bolt holes for clamping. For fabricating, if you don't weld, consider a flat lower .050" steel sheet cover that comes up to the pan, a flat upper .050" cover from the crank to one inch below the pan, then use 1 inch x 1/8 or 1/4 aluminum bar stock as a spacer and bolt together with 1/4-28 x 3/4 machine screws and nylocs with the heads facing the flywheel. You can probably get all that at home depot. Make patterns that fit perfectly from cereal box board before cutting any metal. If you are going to hammer form, don't trim the lower edge and drill to fit the bolt holes until after you have the necessary offset/joggle in the panel.

Rooster, don't you know the safest plane and pilot is on the ground? HA! If safety were actually first, we'd all still be walking. I should have said props with defects or better yet, tell a story. I always see potential aircraft and car projects then remember how many I have stored away and unfinished. Never enough time for it all so I enjoy the moments. They can let it all go at the estate sale. You might enjoy British Top Gear Season 15, Episode 6. They tour the remains of the Jensen and TVR factories. An interesting mix of funny and sad. For the sake of humor, they literally throw together a Caterham as fast as possible in Season 8, Ep 7. https://www.youtube.com/watch?v=cOxHV6QfJkg End of thread hijack.

Imho, old props look good over a fireplace mantle.

Another option would be to pull a fiberglass mold from the steel dust cover, then layup a carbon fiber replacement and notch it. Add some washers and blue loctite or safetywire. Is it also sandwiched by the starter to the bell?

Of course, what keeps oil from moving up usually keeps it from returning to the pan. I could see the benefit of a filler plate across the rear to keep it from moving up the back of the engine during accel, or a crank scrapper along one side that shears oil from the crank, or a mesh screen windage tray, or trap doors around the sump similar to what you might see in a fuel tank, but I don't see any benefit to adding this plate, imho. The original piece is better if this is intended as a replacement for that.

I suggest you take the removed diff to an automotive machine shop so they can remove the broken bolt and clean/chase all the threaded holes while they have it, verify the thread size and pitch. It is easy to make the problem worse by breaking off hardened extractors in the hole. Use copper anti-seize on the new grade 10.9 bolts and shanks. Make sure the new bolts are not too long and bottom out in the diff. Adjust with washers if needed. I'd add a split lock washer and regular flat washer. Mcmastercarr is a good source for hardware.

It comes with a slotted baffle sandwiched by the pan side bolts.

It looks like the glass is custom made for Superformance, so they may be the only source for a replacement. I assume it is laminated glass and not coated polycarb.

Also, http://www.beachmanracing.com/suspension-bushing-kit-pre1990-dedion $127 from USA. If out of stock, just search for "Caterham parts USA" to see many options to check.

So yours is the opposite of this '81. I doubt the bell matters except for possibly the depth available for setup of the HRB. Extra space can be shimmed but too little is more difficult. I'd rather have an external slave setup for easier bleeding and replacement.

I just stumbled across these chaps: https://www.3jdriveline.com/webshop/gear-kits-and-boxes/ford-type-9-5-speed/gear-kit/ford-type-9-straight-cut-close-ratio-gear-kit/ Looks like you may have 2.39 1st. I'd find a used merkur box and try it out, then go through it if you're happy with the ratios.

Set the wrench lower than the end torque so you know it is clicking properly.

Me too, but it was hardware included with a greddy turbo kit for a miata about 20 years ago, holding the td04 to the manifold. Bolts had no head marking. I guess these bolts were new replacements and not the originals?

That would be a very unusual 1st ratio of 2.37 with a 3.9:1 diff and a 22.97 tire od at 8k. There is a close gear set available with a 2.97 1st (51 mph) and the domestic production Merkur T9 has a 3.36 (41.7 mph).

What rear tire size?

Inch/lbs, not foot/lbs. Only main, head, and connecting rods are foot/lbs. Go for mid-spec rather than peak spec.

The starter is on the opposite/curb side for a hydraulic clutch. Why change it to hydraulic?

R888R are available in several 13s and a 185-60-14 that may work for your rim width.