Mismatched serial numbers on block?

[shaneroze]

Doing my first engine rebuild on a 1997 C1500. It has factory gaskets and was never maintained right, and the block serial number goes as a 350 vortec, while the piston in it reads to a 305. Had a broken connecting rod and was going to change it out simply since it didn't scar the block at all and I cleaned the block out. Got two other legitimate 350 vortec pistons and they're too big for it. Everything else on my truck reads to a 350 5.7 vortec as well.

 

[Hipster]

Double check the block casting numbers. https://www.mortec.com/

I'm betting someone replaced a 350 with a 305. What the tags on the core support or rpo codes say doesn't matter.