I have a friend that bought a long block from a reptable machine shop, so I've been told. Th block has the "401" casting ground off the side of the block. The internals are 401, but we don't know if the block is 390, punched or resleeved 360, or what. I thought the 390 had a different deck height and the 360 has different journals. Plus, isn't a 390 worth more than a 401? So why grind off the "401" casting? Is there another way to tell what the block is? If there were no problems with this motor, I wouldn't be asking, but it overheats when towing and he has detnonating problems. He runs regular gas, but with an 8.5:1 compression, that shouldn't be an issue. New radiator and the timing is right on, and even had the tranny checked out to see if that was an overheating issue. Help guys.