All the castings have GM part numbers. I am told it will only bolt up to a SM420 because it replaces the rear bearing retainer on the SM420.
Added another pic:
http://s1253.photobucket.com/user/GMCPic/media/Gear%20Box/14081_58_1.jpg.html?filters[user]=127999858&filters[recent]=1&sort=1&o=0
It was probably only used by Chevrolet, I was informed that all the Advanced Design Chevy s (larger than a pickup)came standard with SM420, that a 5 speed was only a later option.
It only weights 95 pounds...not 200.
