I don't have a 340 so I can not comment on KB 243's, I do have a 360 with KB 107's, I like them. I think they are a good product, pay attention to KB's installation instructions you will be OK. They will take power adders, I have stated in another post, survival is due more to tune-up, not piston. If the engine detonates hard enough to break a piston, you already had broken rings, maybe collapsed ring lands, again goes back to tune-up.
I'll say this, I kinda like the looks of the KB's.......at 184 grams (piston, pin ) less mass from stock, that translates into just over 3 lbs removed from rotating assembly, it would rev like mutant chain saw engine.
