The 1st year of the D150 was 1977. I had one with the 8 3/8 rear axle from the factory. There were D100s with the 9.25. The same transmission was available in both, fuel tank sizes were not dependent on truck weight, alternators were optional, the same spring capacities were available on the D100 and D150, tires and wheels were the same size, the frames were the same, etc.

From the brochure:
*All D100 models include Evaporative and Exhaust Emission Control System. All D150,D200 and D300 models include heavy-duty Exhaust Emission Control System.


1970 Dodge d100/eventually going on a 77 D100 frame