According to Novak's website, 67 was the last year for the SM420, 1968 was the first year for the SM465. The SM420 was still used in some Military trucks into the early 80s though.

http://www.novak-adapt.com/knowledge/transmissions/manual/sm420

http://www.novak-adapt.com/knowledge/transmissions/manual/sm465/


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