Looks like it is a 54, the casting # in the head is 3835913, by the starter it is B 254 water pump pulley looks to be about 4" in diameter, couldn't get a good angle on the gen bracket but I think it was attached near the oil pan ledge. The only external lines I see are the ones that go to and from the external oil filter. There is another plug going to the center of the head, it still has a piece of line sticking out of it that was cut and folded over.
I bought the truck from the wife of the previous owner, who has died. He brought it up here from TN (actually this one and a GMC) put them in his barn and never did anything to them. So, I have no one to ask any history questions.
