Hrmmm. I should say that when we talk about the vintage "rally" it's not really a rally. It's more of a 1000 mile spirited road trip, so the .73 5th gear might be find considering if I'm in 5th on a back road I'm probably going too fast and should really slow down.OK OP. My T5 plans for my 'forever Manta rally car project' (LOL) are to use the Ford T5 WC products. This is simply to get the best variety of gearsets. I have not seen the same variety of gearsets for the GM WC T5 as you can for the latest generation of Ford WC T5's.
You can build a close-ratio T5 with a 2.2 or thereabouts 1st gear and a .83 5th gear if you realy want performance or other sets, like if you want a .73 5th for easier cruising. Just a word of warning from long rally expereince on the stock Opel trans.... the 1.5+ step change from 2nd to 3rd gear really stinks; it occurs right at a critical speed for rally stages and is just too much. So if you want performance, you want to get down at 1.45 or lower on the 2-3 step.
No worry on the clutch for the Ford WC setup; there are 10 spline clutches for the 2300 I4 engine that will work fine with the Opel situation.
1-1/8" thick plate is what you want for the Ford WC trans. I am not confident that 3/4" is what you want with the Chevy WC T5; it has to be a certain thickness to get the pilot bearing set in properly. I think you have better look things over closely before you go with a different thickenss and re-read the published info.
Step 1 should clearly be, figuring out what I already have. I just went to my garage to shoot photos of the transmissions I have, but haven't had a chance to sit down and decipher what they are yet.
There are two sets below, both titles are link to the IMGUR posts if you want to view them in higher resolution
S10 T5 Trans:
UNKNOWN WC T5 Trans: