We used to have a class C motorhome on a 1978 Dodge MB300 chassis, bought the shop manual from Helm ( www.helminc.com
) and sold it [the manual] on ebay last year. The manual is for the vans and the cutaway chassis used for motorhomes. Check on ebay, you might get lucky and find one for your year vehicle.
I still have the 1973 edition shop manual which I bought for a previous van we had. You are welcome to have it for the cost of postage, if it will do you any good.
Good luck with your project,
Just checked Helm, and they don't carry Dodge manuals anymore. Maybe I bought directly from Chrysler?