Until I started the T56 swap, I didn’t realized how much the u-joint angles was a part of this process. It’s been a real eye opener for me. And it isn’t just what angle the motor is at, like you said with the SS springs, the attitude of the car has a huge influence.
Funny thing is, for me to say my motor is at 3 degrees is kind of pointless since that is measured relative to the ground. I need to take an angle measurement on the bottom of the front frame horn where it ties into the TB crossmember. Not certain that is very consistent, but it’s the only place I can find that isn’t sloped. Maybe it would be a useful reference for other people.
I too have heard that the Keisler TKO kits put the tail down to make it fit the A-Body but wouldn’t have guessed you would need 3/4-1” to get it right. That’s a bunch.