I think that the general consensus will be that the 318 heads will be okay for low rpm use but from 3000 rpms and up, they will pose a bottleneck to flow. Finding decent 360 core heads isn't easy. I had similar problems in 2008 when I was looking for good 360 heads for a build. I went through 15 heads before I found a pair on the same engine that were NOT cracked. After taking the 3rd pair to the machine shop for magnafluxing, I started popping the valves out at the junkyards and looking at them with a magnifying glass. It was a real pisser. Now there are better choices. Have you heard of EngineQuest? They make NEW Mopar small block heads that flow better than stock heads and are somewhat affordable. Good Luck.