**Milling .030 off '920 - 273 heads**

Your 273 heads will need to be milled .040 to get down to 57 cc's. I always mill the intake side of the heads, .0095 on the intake side per .010 on the block side, so only the heads have to stay together and you can swap intakes whenever you want. Not sure you will gain anything by the head swap. I've always run the Felpro gaskets and never noticed a difference in power using the larger bore gaskets and they don't leak. I used steel shims under the rocker arms to get the right geometry after milling the heads and running a 340 cam and rocker setup. I prefer the solid cam and rocker setup though.