The thing that jumps out at me is the compression. Did you actually measure/calculate it yourself? The reason I ask is that it's mentioned that TRW flat tops were used with J-heads. If you take a flat top and install it at zero deck height, assume a 0.041" head gasket with a 4.100 bore (since most are made for 340/360)...it takes a 62cc head to get to 10.47 to 1...which a J-head is not. J-heads tend to run 68-72cc. Also, most flat tops have valve reliefs of some kind...and I know my Wiseco's are 5cc's. If you have 5cc cut outs in yours, then you now need a 57cc head to get to 10.47 compression. I don't think you can cut that much out of a J-head.
The set of J-heads I have measure at 69cc. Using THIS volume plus the above numbers, you're looking at 9.1 to 1 compression. That's a bit on the low side for the cam in the engine. I'd DOUBLE check the compression as a starting point.
