Mine would be an El Camino with a Duramax. Of course the frame would have to be strengthened. It is low and can haul motorcycles and big parts in general and maybe a small trailer.
My friend had an El Camino on a K frame with a 454 like this one. It was basically a streetable monster truck.
Vans are always good choices and so are trucks, but is there something else you guys would use?