Big block rebuild - where do you buy your parts?

Felpro gaskets, and

If you can afford a .030 you can run these forged pistons and gain some compression height. Yes, a full set of forged pistons for $120, and you can even use the 20% off on them. I did.

https://www.napaonline.com/en/p/SEPL2315NF30
These are what you want