Which PTO Model or Part Number Do I Need?

Hi, someone has recently posted they have about 35 pto's they're selling. I might be interested in one of them, especially one of the multi-speed pto's.
How do I know what to tell him is the model number of the pto I need for my IH 5-speed trans? Are all 6-bolt pto's, for the most part, interchangeable? Does every pto for every transmission type or manufacturer make and model of transmission have a different pto model number?

My good truck has a T-36, code 13-036 and my parts truck has a T-495, code 13495 five speed transmission.
Thank you.

The cases are all the same, the guts are made for the transmission it was built to fit. I don't even bother buying a used one. You could and then have to replace the guts to match the transmission, unless you know it came from the same model you have, it isn't worth the trouble.
I have a one for Eaton Roadranger's and one I have no idea what it fits. (came in a box of junk).
The IHC 5 speed takes different set -up's for left and right side.
When you add to that not only do you need the correct trans, you need it to be the correct speed and rotation.
By the time you get that sorted out, buying new seams easy and not so expensive.

Yep, that makes sense and that's what I kind of assumed. I expect I would need to disassemble and clean it, but unless I knew exactly the transmission it came off of, chances are good its not going to fit an IH 5-speed trans.
I'll just wait until I'm ready for it then buy new.
Thank you.
For fun, here's a picture of his pto's:

It is unfortunate that who ever removed them, didn't tag them. I think if you knew the maker and they were still in business, you could decode the trans, direction and operating speed from the numbers on the tag. IIRC it is quite a long number (from when I put a new one on) and all digits and letters must be readable.
Eaton' Roadranger series for a while anyway, made it easy the cases were the same and they had dedicated PTO gears that had the same tooth profile and count. You could pull a side or bottom PTO off one RR and put it on another.
Most single countershaft transmissions, use another gear on the countershaft to also drive the PTO so there are hundreds depending on profile, depth, etc.
That is why, when they get thrown in a pile, they are more or less useless.

https://www.munciepower.com/software/power
Might help