Building a 340 engine

When picking heads pick your rev range first
that will determine cam lift
then get heads that maximise the lift you are going to have
getting heads that flow big time at high lifts frequently give up flow in the lifts a street build can use
rocker ratio helps but roller rockers + B3 kit gets pricey and 1.65 can be done but also pricey
Magnum heads can go 1.7 but 1.6 is free