[Yosemite Sam]

I understand your dilemma, if I had a PTO rear end, I wouldn't know what to put it in either.

Since they don't really do anything, do you put it in a tractor that you use regularly or something that sets around most of the time?

If it were mine and I intended to use the whole trans-axle, I would want to put it in something that corresponds with the serial number, just to keep everything original.

If I were going to use just the parts, then I would put it in whatever I wanted.

Either way, a rear PTO would be a cool thing to have.

Good luck with whatever you decide.