I don't remember whether the engine tilted, and the car is in storage well away from where I live, but I do recall that getting the right pinion angle was an issue.

If you don't get that right, you'll have a vibration problem.

Here is my video. Does your engine lean slightly back?
http://www.youtube.com/watch?v=JPpfdCPeG8Y

Hey man I saw that you installed a TKO 600 in your firebird. I just installed one in my 70 Trans am. I noticed the engine and trans are tilted back about 3 degrees. Is that how the engine normally sits? Leaning back about 3 degrees? Or do I need to make some sore of spacer to go under my trans mount to raise the rear of the trans. Problem is if I do that I will have to cut the trans tunnel for the transmission to fit.