I believe all of the SM-420's have the same bolt pattern so they should bolt right in.

Also, your '57 3100 has parking brakes at the rear axle, so the transmission you're looking for doesn't need the parking brake drum or hardware on the back.

Mike B smile



Mike Boteler

1956 Chevy 3100 Resto Rod
1952 Willys M38 Army Jeep
1983 Jeep CJ7 Laredo
1984 Jeep CJ7
+++++
Silver Spring, MD