A V8 chevy engine is designed so that when the carb mounting surface is at zero level, the trans output shaft will be 3-4 deg down. When mounting an engine focus on the carb mounting surface as you fab engine and tranny mounts. Then try to get the pinion shaft parallel to the output shaft of trans (3-4 deg up). All this should make the pinion to driveshaft and the output to driveshaft angles the same. (and hopefully 3 deg or so). Don't forget to phase your ujoints if building from scratch. You don't have to be super accurate just pretty close, after all, the rearend rotates up as torque is applied.

Right is right, even if everyone is against it, and wrong is wrong, even if everyone is for it. - William Penn