Cummins mpg vs 225 Slant 6 mpg
if you need a daily driver thats a truck buy the cummins, the slant truck is underpowered and even more underpowered with a load on. lucky to get 15 MPG
the factory cummins trucks are 3/4 ton, if the 82 isn't look elsewhere, nothing in a 1/2 ton is strong enough to support the cummins engine
plus side is the first gen cummins engines 1989-1993 got 20+ MPG and rarely need any work, they can run 500,000 miles without much work just the simple filters and oil changes
the diesel will get the same MPG loaded or empty, and climb hills the same