360 heads on a 318, I know it has been beat to death...

Head milling to reduce chamber volume

a. 340 - 360 heads

To reduce the chamber volume, remove .0048" from the head surface per 1 cc of chamber volume.
For each .010 removed from the head, .0095" must be removed from the intake face of the head.

273 - 318 is the same except the .0048" is change to .0053". Thats it.