More than any other single question, this one comes up the most. The Chevrolet Truck serial numbers are well documented, but us GMC guys are left out in the dark.

GMC - The Numbers Game by Ron Dettling For those of you who rummage around wrecking yards, swap meets or other likely places to find basic GMC engine parts, blocks, cranks, heads, etc., it is highly frustrating to find a treasure that you know is GMC, but which you can't easily identify. Sony Acid Pro 7 Plugins Free Download there. Unfortunately, even knowing the GM part number is not helpful, since the major pieces are not marked that way. The following list of casting and forging numbers may help in determining your degree of interest in a particular part. The information came from several old books, and show several crankshaft forging numbers for most later engines. I don't know what the differences are, but it appears that they are interchangeable. If any Inliner has any further information I'm sure it would be of interest to others. *** Important note on GMC head and block interchange**** There were several combinations of pistons - flat-top and domed - to match a variety of head configurations.

All GMC heads have the same bolt pattern and port spacing, so any head will fit any block - BUT unless you have the correct pistons to match the head chamber, you will have problems such as inadequate compression ratio or worse, valves hitting top of pistons. Be sure you use the correct combination!