47 was the first year for the SM420. Here is a link to the info on that tranny. http://www.novak-adapt.com/knowledge/transmissions/manual/sm420
Congrats on the new truck! I'm trying to get another as well, if the guy will ever call me back!


Mike
1955 Chevy 6400 ex-flatbed (no bed now!) sold September 2023
In the Stovebolt Gallery
1958 Chevy 6400 flatbed W/dump
In the Stovebolt Gallery
1959 Chevy Suburban Owned for almost 20 years, Daily Driver -- sold May 2016
In the Stovebolt Gallery

Sufficient unto the day is the evil thereof