Planning to build a hotrod frame, Ford rear axle has a 2" offset pinion. Does the motor/trans need to be offset 2" to match or can the drive shaft u joints manage this little difference?
Driveshaft length matters, as to your ? Offset if: you have steering box needing room in left front region. See recent thread on driveshaft-u-joint angles.
Can you explain? My thinking would result in the opposite. Draw 2 parallel lines on a piece of paper about an inch apart. Put an X on the left hand line close to the top. Start at the bottom of the right line and place a series of X's a couple of inches apart going up the line. Now, using the left X as a pivot point run your ruler across each of the right hand X's and observe the resulting angles.
Irrelevant, provided pinion centreline is parallel to engine / transmission centreline, provided that engine / transmission centreline is parallel to centreline of frame. Many manufacturers have off set pinions and not every car / light truck has a centred pinion. Your rear axle needs to be square in frame, measure with a trammel bar if unsure and frame is square, check diagonals. Also ensure pinion angle is correct and corresponds with engine / trans angle. I won't go into detail as it's been flogged to death like a dead horse here on the forum. The longer the driveshaft, the shallower the arc. https://www.dragzine.com/tech-stories/pinion-offset-guide-and-how-to-with-chassis-engineering/
Simply put it's not a problem, ford has been using a 9" how many years ? AND they've been using them with that same offset since day one. Ford doesn't offset the motor either, the drive shaft offsets to the side in any ford with a 9" so that means you can do the same thing ford has been doing too, center the motor in the frame, center the rear end in the frame and enjoy.