Lets assume big block, distributer in front, right? Then there will be a machine surface to the right of the base of the distributer, is that facing straight up? Probably. Next look for some stamped numbers on it that will tell you displacement. If the machined boss is under an a.c. Compressor it might be hard to see. If the machined boss is at a bit of an angle facing more towards the top of the drivers fender that's ok too, it will also have the displacement stamped on it. If the plugs are coming straight out of the valve covers, walk away and give me the owners contact info.
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