I answered the guy on the other forum, but if this is a different question, here is some info
The tough part, if there is one, is measuring angle not knowing where it started if you already took it apart because you need to do some figuring. What I do on Toploader conversions is measure to the floorboard at the output shaft before disassembly (driveshaft and yoke out) and then start there with shims when I put the TKO in, needless to say it's usually spot on unless I need to make room for the tranny. Better said, it's no worse than before.
FWIW, I haven't seen an aftermarket Mustang crossmember that hasn't hung the tranny too low. I drove mine up 3/4 more than the crossmember to get back to stock angles, but that also required some floor work. However, Bruce Couture at Modern Driveline sells machined cases now that let you drive the tranny into the tunnel, my guess is that he has raised the mounting pad on the crossmember or provided shims to get you there. We should have one in hand over the next year, but I haven't seen his stuff yet
At the opposite end, If someone just trusts angles and runs it, of course u-joints can suffer, people talk about that all the time, but you may see some immediate feedback at the bottom of the fan when you tun the key too. SBFs are different than FEs and it gets pretty tight at the bottom if too much angle
