You need more compression and cam and better #'s out of those Indy heads.
I ran a 425 W5 motor with 14.32 comp heads flowed 331 at .700 ran a 1.6 roller rocker W5 large runner intake Erson roller
[email protected] .450 lobe ground on a 108ls and degreed it at 108 and TTI 1 7/8 headers.
69 Dart ran...