If it's got a V6 it will be a GMC. Those engines were standard in GMC's from pickups to heavy duty rigs, anywhere from 305 cubic inches to 478, I believe. There was also a 351, a 401, and a couple of other displacements. They're big, powerful, high torque engines with a huge thirst for gasoline. There should be plenty of room for a small block V8. He will have to fabricate motor mounts, as there won't be anything available as a bolt-in conversion.
If that V6 engine happens to be a 401, that's the same size my 61 GMC American LaFrance fire truck runs. Does the truck also have a 5 speed transmission? Mine has a Clark 5 speed with direct drive in 5th. gear. I'm looking for an overdrive 5 speed. Check inside the glove box door- - - -there should be a data plate with all the truck's vital statistics on it.
Jerry
