Converting my project 1971 Coupe was a factory base 350 auto(TH400) got it missing engine/trans..  Got myself a short block 454(468) bored over .60 and desided I'd like a 4-speed Muncie in her. Got a 27 spline M21 and now in a quandry about drive shafts and yokes, etc.  I have my original differential 3:55 with standard yokes and I have the 1/2 shafts 2 1/2"  But I bought a pair of 3" half shafts for it a year that need restoring. Been seeing all sorts of parts out there original and after market. I have a slip yoke for the M21 output that has press in u-joint caps but it seems small to me, came out of another Vette with a Muncie M21 not sure of year though. Should I upgrade my diff side yokes to heavy duty with the big caps and bolts? Standards use u-bolt style. Half shafts look as though they'd fit into the standard side yokes. Maybe go with 3" half shafts and standard u-bolt style yoke already in the diff?  Use what I have for the trans driveshaft and slip yoke, just go heavy duty u-joints all around and be done?  I don't think I'll be going beyond 2 steps up at best from a stock 1970 454 power and torque wise.

Our cars cannot use a trans yoke like that. The trans yoke must be of the bolt/strap type for the u-joints. There's NO way to install the driveshaft into the car with a regular, pressed cap yoke...just can't be done, unless you want to remove the engine & trans every time you need to service the u-joints, driveshaft, or even change the rear seal of the trans.