Well I finally got the time to root around my 73 F350 CC longbed that I bought in April and I was underneath the truck looking at the bottom of the eng and I see a ID tag on the side of the block that reads AC DELCO Engines, Remanufactured for General Motors, it gives the Bore and stroke, main bearing, rod bearing specs. This is a FE390 eng because I have 3 of them and I know what they look like but what I'm confused about is why that ID tag is on the side of the block. GM & AC DELCO did not produce 390's. The only thing I can think of is the previous owner had trouble with the eng and took it to a GM dealer and they ended up replacing or rebuilding the eng and when they were done slapped there ID tag on the side of the block. Does anyone have any insight on this?