How many versions of the liftable rear hitch were made? Is it generally interchangeable between the 800/8000 & G tractors? Also, with respect to the axle block, were there two versions: one for non-tapered axles and one for tapered axles? I'm looking at an 8163b with a liftable rear hitch setup I'd like to transfer over to a G series. Is this doable? Ditto for the axle block?