The "inliners" link provided by Gord above indicates that casting number used for 1948-49 for Chevy 216s. The pictured serial number sequence does not match the ranges listed (FA for '48 and GA for '49).

Serial number could be something by previous owner(s) as engine not original to your GMC. Anybodies guess how it came about.

At least you now have the basic engine ID info to help when needing parts or reference information.

Have good rest of your weekend!

Dan


~ Dan
1951 Chevy 3 window 3100
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"My Grandpa Carl's Truck and How it Became Mine"
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US Army MSG Retired (1977-1998) | Com Fac Maint Lead Tech Retired (1998-2021)