Opinions on a 340

Simply not true, but given the reality of parts vs manual stated compression, that 340 is closer to 7.8 than 8.5:1. It's a weak point. Add to that the lack of any valve reliefs it makes camming up later if he wanted to a problem.
If it were me, I'd run the hypereutectic pistons as Swinger mentioned, have it rebalanced and the heads and deck set up to give an honest to goodness 9.5:1, run the rest of the stock parts with the exception of the cam and valve springs, and will get 375-400hp from it on any pump swill you find.