i think it has nothing to do with the starter. both will interchange with each other. but a bent piece of metal will not hold the torque of a flat piece. thus the 80e flexplate is flat with a spacer and the 60e is reccessed in the middle.

 

The converter for the 2 trans are different. The 80e has the snub closer to the housing, while the 60e snout sticks out a lttle further, that may be backwards too. THat's why the spacer's used though. The recess in the flex plate is so the teeth will line up with the starter. If it weren't for that recess, then the teeth wouldn't hit the starter, so they would have to have 2 different style starters.