I have a 1980 crew cab dually, and i cant find hardly any info at all on these things. Does anyone have a clue on how many of these things were manufactured?

 

Sounds like me. I have a 1971 Winnebago and it uses the D-300 running gear. also a dually. I think I found te engine wiring schematic and teh body schematics finally after over a year of looking.
It has nothing to do with Mopar but I need to find the MH wiring and water,sewer,propane schematics so if anyone can help that be great.
Try going to Autozone.com and enter the vehicle info and browse their technical info section you may be able to find some good info that was where I finally found teh schematics I was looking for?