Thanks, I was kinda hoping that you had a simple fix! Changing inputs shafts wouldn't be a problem, I have a couple of them laying around, but I hadn't thought about the spacer. What about machining the flywheel to take up some of the space? I don't have a feel for the difference in depth from the single disc to the double, is it 1/2 inch deeper or inches deeper? I have a few inches of radiator fan spacing, so that could actually help fix one problem. PTO shaft length sounds problematic.
On the O/U issue, I'm planning to go with the thinner Kolene steels and the extra frictions set up like in the 2-180 heavy duty. Gonna use overdrive frictions made to carry higher HP than the agco parts. Planning to shim the pressure up. It seems to look good laying in parts on my bench, we'll see how it works once I figure out how to get it bolted in the tractor.
I'll be pretty disappointed if we bolted it all together with the single disc clutch and ripped the center out before I figured out whether or not my O/U modifications were any good.