Gearing question

Hey GUP,
It is hard to figure anything without knowing what the weight of your car is. If you could post that, it would help. I will give you a little run down on the car I have been driving for a guy that might boost your thoughts a little.

1973 Plymouth Duster, 2750 to 2800lbs...depending on driver
446 cu. in. 9.5:1 compression...Was a stock rod street motor
915 heads 1.6 ratio crane roller rockers, some porting
310 x 585 straight up...Big block has all the torque it needs down low, don't advance your cam. If anything retard it.
Holley Street Dominator intake, been milled and handworked for Dominator Carb
1050 Holley Dominator Carb
727 torqueflight w/ reverse cheetah valve body, 4800 stall
2" headers w/ 7" collectors...Long collectors build torque (not needed w/ big block)
4.86 pro gear, coil overed, 8 3/4, ladder bars
12.2 x 32 Hoosier Slick
This car runs consistent 10.80's all day long..Last time out we run 1/8 mile and it run from 6.94 to 6.97 all day >>> maybe this will help...Sounds to me like your car has a lot left in it w/ better combo....Probably as 340 dart and ramcharger said...Your car is running out of breath (out of cam and cfm) gears would probably help a bunch or a taller tire to get the motor backed up some...Just my 2 cents...Lee