GM Block Casting Number

[Baby John]

I think I've been duped. When I bought our truck I was told that the engine was a brand new crate motor. Yesterday while degreasing and cleaning up the frame and engine, I scratched the grease off the block and found the block casting number 3970014. Did a little searching this morning for "Decoding GM Block Casting Numbers" and found two website that listed this casting number. One had this number categorized as 68-79, and another had it listed specifically for 1972. So, since my old truck is a 1972, I'm thinking that this SB 350 is the original motor. Possibly re-built, but not a brand new crate motor like the PO told me.