I have a nine in ford center section with a 2.75 x .500 wall tube in it that I put thru the block main bearing bores. With the rear end at ride hight, I position the engine so that the crank front center is whatever height that I want with front end at ride height( 3 inch NHRA rule) Usually consideration has to be made for pan and bell housing clearance. This will give a drive line that is straight from the crank thru the pinion shaft. On car set up I will then adjust the pinion down from 1 to 3 degrees as it will want to lift thus sraightening the drive line under power.

Jerry