PTO question on John Deere tractors

I was wondering when John Deere changed the size of the PTO. I know that there is a 540 with 8 or so spines on it and than there is the 1000 with alot more spines. I have been told that John deere has different size PTO's in thickness when you get to bigger horserpowered tractor. For example...if I have a 4455(150 hp) that I hook up to my baler and I go and buy a tractor with 180+ hp that it will not hook up to the baler because the pto on the baler is too small to slip over the pto on the 180 hp tractor. Can anybody tell me if this is fact or fiction.

I haven't really looked into this much myself but I figured I would get some other peoples opinion on this matter.