engine combination

it has a 904 trans with a 8 3/4 sure grip rear with 3.91 gear, with 255/60r15 mickey Thompson drag radials. I thought it should be faster to. also it has tti step headers with a 750 double pumper holley. my 60 foot time was 1.90 and my trap speed was 103. but even if it runs mid 12's I want to go faster and I already bought the heads so just wondering if the heads and cam will make goo power with my combination. I would like to run mid to high 11's if possible. and I made 3 passes and they were pretty consistant.