What engine would you build for a Ramcharger?

I think with 3.21 gears, and a 31" tire, and of course they have tight converters, I would use the 360. It sounds like you are going to be under 3k rpm's pretty much all the time. The low end grunt of the 360 is what I'd want. Under a load all the time like the RC will work it, the 360 may even offer better gas mileage.