Looks like the 650 used what Deere just calls a 60 inch deck. There a LOTS of variations seemingly without specific model numbers. Differences include gearbox offset or centered, driveshaft front or rear, gauge wheels, mounting kits, and much more. The 650 uses an optional electric clutch belt drive off the front of the engine to a driveshaft below it. The 650 mower gearbox would need to face forward. Finding a few pics of it indicate it did not have a left front wheel. You will need to find exact details from a dealer. I don't see anything on JD Parts. I also found several tractors with a Woods F35 deck. That did not use a driveshaft but ran a long belt from the PTO shaft. Good luck on finding any deck for the 650. An original one would be quite old and typically very beat up.