So, I pulled the trigger on the Sadev sequential gearbox this morning. I ordered it from Mog-Racing.com in Germany. The same place I got the Nitrons from. They were great to deal with. Apparently, they are now a Sadev distributor and have created a true plug-and-play setup for a Caterham. The kit included the wiring harnes, GCU (gear control unit) and gear position indicator. MOG-Racing had a Sadev (with the 1:1 final ratio) in stock so it won't be long.
So... this leaves my Caterham 6-Spd up for grabs, in addition to the motor.
I plan on explaining to the wife that it's nearly an automatic, no need to use the clutch or even let up on the gas to upshift!