Hi Ted, I know the front steps/pilots were a different design from the prewar to the 1615. The front steps pilot to the 1989 re-release looks very similiar if not identical to the 1615. There was also an article in Toy Trains magazine years ago about converting prewar box couplers to post war knuckle couplers. I try to keep my prewar switchers with the couplers they came with (mostly the prewar box, but a few with knuckle couplers) and this way I have some flexibility...but that is just my preference.
Tom