You know, in 4x4 circles the Toyota axles have a better reputation than the 10 bolt stuff for durability behind 'Merkan V8s.
If the Supra axle is the same as the axles used in the Toyota mini-trucks from the mid-late 1980s it may be worth hanging on to regear and add a TAD after your 10 bolt goes boom.
Your car being light compared to a piggish F-body that may be a long time though.