My mild 360, .040 over, around 9:1 cr, stock stroke, stock heads, hyd flat tappet cam, with an Edelbrock air gap and 750 carb, running a .444/.467 cam, TTi headers through a full 3 inch exhaust and a 727 trans and 3.23 gears in a full steel body, full interior 1970 Dart ran 13.80 @100 mph 1/4 mile.
I don't believe that motor made more than about 350 hp.
My mild 360, with OOTB Eddies, 11/1 Scr, a 223/230/110 Hughes cam, a 4-speed and 3.55s, dressed otherwise like yours, ran 12.9/106 in a 3650# pound 68 Barracuda, on the one and only run it ever made. That translates to 335hp.
That cam was 270/276 advertised.
Not a hope in hell are my stock Eddies plus the compression difference, worth 75hp.
I don't believe your engine is up to speed yet, unless your Dart is way heavy. To go 100mph at 3400pounds, the Wallace says you need 262 hp.
But at 3650 it requires 282 hp.
Trapspeed is very little affected by modest changes in street gearing.
There are many things that can be choking your power.
IMO
You're gonna need to do some hunting.
Start your own thread; there are lots of FABO members here willing and able to help you track it down. Your engine/chassis combo has the basic ingredients to get into the 12s. Start with the basics; Do a compression test followed by a Leakdown test.