I agree with others, you need more stall, I think it needs more carb too. Did you dyno the engine? Have you tried less timing? My Indy headed 434 made the most power at 34°, any more and power fell off. I'd talk to your head guy about converting the intake to a dominator flange.

IMHO your 60' and 1/8 mile et and mph are down too. My street/strip Dart has been 6.25 @ 110 and 10.008 @ 134.75 on pump 93 at 3293#, foot braking at 2000 rpms. it went 6.33 @ 109 in street trim last fall. The engine is 4.125" stroke and 4.09" bore R1, 11.2-1, 266/271° @ .050", .711/.719" at the retainers, ported Indy 360-1's and ported Indy intake, a 1050ish Thumper built 4150, 1 7/8" Hedmans. 727, Coan 8" that flashes 5600, Strange S-60 with 4.10 gears, Cal-Tracs, monos and Viking D/A all around. It's currently on a 275 radial, but previously was on a 325 radial. The engine made peak power at 6750 on an engine and chassis dyno, I shift it 68-6900 rpms.

I think my car will run well into the 9.90's in decent conditions. With some tuning you should run a couple tenths faster than mine. Keep after it, you'll get there. Great looking Dart too.