The 1260 came standard with draft control (which is one of the pieces to this puzzle) while it was an option on the 1250 (one other difference is the 1260 has an oil cooler). If your three point control was just one lever, you don't have DC.
Thanks for the pictures, I have enough for now. I'm trying to find out now what the deal is with the two port manifold block which doesn't seem to be in any of the AGCO parts books for the 1260. I'm thinking it came off another tractor (prolly the one the loader was originally on) and the previous owner pressed it into service, but that's just a guess.
