1977 dodge sportman

Well, you can head to the parts store and look for a Haynes and a Chiltons manual. I prefer Haynes. What size is the van you want to modify? On the fenders, right in front of the door is an emblem. It will usually have a number following a letter. Being a van, you have a B series. This is NOT a class B, but the series B vans. Look at the engine to see if you have a small or big block engine. If the distributor is in the back, it's a small block. If it's in the front, you have a big block. Usually, these had small block engines. There will be a plate in the drivers door, either on the door itself or the door jamb, that will tell you the engine, transmission, rear and front axle capacity and gear ratio in the back, at least what came from the factory.

If you want a roof a/c, you'll need to use 120. You can't get a heavy enough inverter to run that big an appliance. Plug in inverters will run a computer, not an a/c system.