Hey Adam, I think a trip to the local Mopar dealer to talk to one of the better mechanics would go a long way into determining what is needed. Once you new, you might be able to get the parts cheaper at the local pick-a-part.
Don't think you will get any help there. A v8 wasn't offered by the factory from 87-90. There were a small number of trucks converted by Shelby but that was it. It was 91 when they redesigned the nose of the Dakota specifically to accomodate a v8 that
The biggest issue is getting the v8 to fit. The Gen1 Dakota has a flat nose and the extra length of the engine is a tight squeeze. The Shelby trucks used an electric fan mounted infront of the radiator.
I would look for someone with a Shelby Dakota and see if you can get some pictures.