82143A and 82162A printer mechanisms interchangeable?

[Dave Britten]

I've got an 82162A (HP-IL) printer that is about 99% working, but for one reason or another, the bottom row on the print head doesn't really register on the paper all that well. It appears to be uneven pressure against the paper, though I can't tell if it's due to a misalignment in the head itself or the platen. I took the head out and cleaned it with a little alcohol, and I can get the bottom row to print if I fiddle with the platen a bit and align it better with the head.

Is it possible to simply swap the whole mechanism with that of an 82143A? I noticed that the optical encoder on the main shaft is a different design, so wasn't sure if they're 100% compatible. But if that's an option, I could just exchange the mech with one from a spare 82143A that produces more even printouts.