My 340 build

On that mag article
no idea if they dialed in the valve train geometry with those custom 1.7 rockers
I used to run the Erson 1.75 Iron rockers successfully
unfortunately Erson destroyed/ lost the tooling a long time ago
did take some grinding for pushrod clearance
since then the "Engine Master" builders have more experience with high ratios and shorter cams to fit those rules
I'd look there if any instabilities