OP asks if a 70-71 wiper motor will work with a 72 Challenger. No, but the odds are high with the 72 Challenger that he has a 3431102 drive link and 3431518 crank arm (although we don't know, the OP doesn't offer that info). The output shaft on the 70-71 has a larger diameter 5/16", .329 wide and is .370 tall where the output shaft on the 72-74 crank arm is 1/4, .265 wide and .489 tall, therein lies one of the problems. (Actually....its the threads and nuts that are different not the shafts. The link has bronze bushings to accommodate the 2 different size cogs....hence two different links that don't mix with 2 different crank arms)

In 1972 Chrysler went to the small latch and if you had a mid 68 to 71 anything with a 3/variable speed and ordered a gear and latch package after they ran out of the early style....you got the small cog cause it was engineered to work on all the earlier 3/Var spd motos from mid 68 on up. Some people think it's not right to put that combination together, but Chrysler did it.

If I were the OP and I'm going to assume since he has a 72 Challenger, that his drive link is 3431102 and the crank arm is 3431518. Rather than replace my drive link and my crank arm to do this conversion, I'd simply remove the switch plate, replace the gear latch/output shaft with a small diameter gear latch (short style) replace the switch plate cover with the correct timing for my E body and be off to the races installing that motor. Cheaper, less aggravation and less time involved.

If the OP has the 70-late 71 drive link (PN 2822293), easiest way to handle things is to get a 2822289 crank arm with the 70-71 wiper motor and he's off to the races again...it ain't rocket science?