[James670X]

The 1ton crew cab dually was made in the old body style from 1973-1991 (designated as either C=2wd or K=4wd from 1973-1986, from 1987-1991 designated as either R=2wd or V=4wd), the 3/4 and 1ton single rear wheel crew cabs again were made from 1973-1991 (see designations above), however I have been told that pre 1977 4x4 single rear wheel 1tons were not factory built rather they were Napco conversions, therefore they are quite rare (some people call HD3/4tons 1tons).
The First year of MPFI (multi port fuel injection) was 1996 (Vortec). 1987-1995 they were TBI (throttle body injection).
The Blazer/Jimmy, Suburban, 3/4ton crew cab, 1ton reg. cab dually (some of them), 1ton cab and chassis, 1ton single rear wheel crew cab, and finally 1ton dually crew cab remained as "old" body styled trucks from 1988-1991.