340 & 360 Cylinder head CC specs

Head cc total determine static compression ratio. I've read Mopar rated them a t 63 or 65 cc so you could blueprint them to 63cc / 10.5 compression and be NHRA legal. Stock they were all around 72 cc's and about 9.5 compression.
Those are NHRA minimum specs. It takes approximately .040 mill to get that small.