fuel pump problems

[crosby]

I've got a friend who just bought a really nice 71 stepside, and he's having trouble getting it running. Apparently, they keep putting fuel pumps on it (mechanical) and they keep getting toasted after about 15 minutes. They seem to be breaking in the middle, at the diaphragm, and separating. The previous owner is telling him there is too much pressure because one of the valves is stuck, and fuel is backing up in the pump. Is that even possible on a mechanical pump? I figure any excess fuel would just get dumped into the carb. He says the engine does sound like it's running on 7 cylinders, and doesn't idle at all. I am guessing they have the wrong fuel pump and/or pushrod. I suggested he find the casting number on the engine block and be sure of what he has next. Even if the cam had worn enough to affect the fuel pump, I would guess it would just not pump as well. By the time you wore the cam down enough to stop the fuel pump from working, the rest of the valvetrain would be long gone, right? Lastly, what about LT1 heads? The previous owner told him the truck had LT1 heads on it, the oldest story in the book. I can't count the number of cars and trucks people sold me that supposedly had LT1 heads. I always thought LT1 heads were aluminum? How can you identify them? Just by casting number? Thanks very much for any help you guys can provide!