A500 is 904 based, 46 series is 727 based. It is said you have to chop up the rear floor area some to allow clearance for the 46, and can get away with "not" on the A500 (42/44Rx) You probably know that rh means hydraulic, and needs no computer, but I've been told that you can convert an re (electronic) to an all-manual valve body.