If we want to build a cost effective 340
and are going to use open chamber heads
snd the power is going to be in the heads no mater what else
one question is- is rob doing his own rods?
If so MP bolts and be done- but pistons?
If buying rods
you could use the 408 1.460 ish CH dish pistons and 6.5 inch (ish) rods and mill the open out of the chambers
or push the piston up into the chamber or some combination looks like 10:1 with a shelf JE piston ending up with a nice tight chamber
what other combos work?