When the motor had 915s on it we ran AR73 gaped at .035.I like the cut back electrode on the AR plugs I think there is less chance of detonation with that style plug.
Bud www.wildcar-go.itgo.com 64 DODGE 60' 1.433, 1/8 6.38 at 107.4, 1/4 10.08 at 132.02 foot brake, leaf springs
