I am far from an AC expert. I do know that transmission and clutch issues on the 7000 series AC tractors can be costly to repair. With there lower value be careful and makes sure what the trouble is before you buy. You can easily end up with more in it than it is worth. They sell in the $3500-4500 range around here in full working order. ( Usually no AC working) LOL
Personal experience with an AC 7000. Landlord had one as his "big" tractor. I helped him do field work some times. That AC 7000 had the worst cab setup know to man. The gear shifter between your legs with a bend to make it easy to catch your foot on it. Then the stupid narrow doors with the steps angles the wrong way, made getting in and out of it a bear in winter work cloths.