I had a JD650 to which I installed a JD60 loader. The loader physically fit, though required hydraulic connection changes to work. Though I could remove that loader from the tractor, it was a lot of work. Happily I had little need to do that. From that effort I learned to get a loader which was intended for use on the tractor you intend. There are too many peripheral factors which can eat up your initial installation time, and then later re n re time. The other factor I noticed with the 650, and other compact tractors with loaders was the stiffness of the loader from on the tractor, particularly when it was a removable loader. Though I used the primary mechanical connection of the loader frame to the tractor as JD designed it, it was not a very stiff loader on the whole. The two vertical arms would bend in and out as a load was lifted, or you pressed the loader down. Not unsafe, but a nuisance. I did consider doing away with the removability capability entirely, and just welding the whole loader frame together to bolt onto the tractor, but I was worried that that would just transfer the flexing loads somewhere else, and it would break. Them that bends don't break! Ultimately, and very sadly, I lost that tractor in a fire, and the insurance company very kindly bough my a new JD1025R. It's loader design is far superior to that of the 650, and the several things I did not like of the 650 loader arrangement are well resolved with good design.
If you're getting a deal on the 755 and loader fair enough, but unless it's a deal, I'd certainly buy an newer JD compact tractor with a newer loader instead!