Did 1970-1972 Chevy 402 Trucks have the VIN stamped in the block from factory?

[HeavyHauler]

I am trying to figure out if my friends 1971 Chevy truck has the original engine that it came with from the factory. For 1970-1972 Chevy truck 402 big blocks did GM stamp the VIN on the block?

If GM didnt stamp the VIN on the block for 1970-1972 trucks then how do you really know that you have the exact engine that it came with from the factory unless you are the original owner?

Another weird thing is that the truck has 400 badges on the fender but has 396 for the engine size on the SPID sticker. He claims it is original but it seems like it probably came with a small block 400.