Your suggestions please, I am jonesing to build.

I would take the top end apart on the 340 and get the measurements,cc the heads,pistons,check deck height ect.Once you know these things you can make some decisions.I would ditch that cam and go with something in the 230 range @.050 with a 110 lobe seperation.You can add a few ccs to the heads by properly removing small amounts of material and polishing the combustion chambers and not mess with quench.With those small changes you could loose the 25-30 psi you need to be fine with a good tune.