High 7's in the 1/8..how much weight and power??

my 67 belvedere runs 7.50's to 7.60's at 3550 lbs with me in it, and 60 ft times are 1.61 to 1.65's. motor is 440 with 10.1 compression, rpm performer intake, 1 3/4 in heddman headers, unported 452 iron heads, purple shaft .509 cam, 4.30 gears, and a 27 in. slick. engine only makes around 425 hp according to the Mr. gasket hot rod calculator.