61 help

[61apachespeed]

hey i have a 61 apache with the 55t rear end. i think i have bigger then 390 gears. i can only do about 55-60 at 3000 rpm down the free way. i found a place called us gears. has any one use them before. cause there about half the price as the other one. i have a 327 and 350t if any one the same set out i would love to know how fast you can go. the few people i have talk to say i should be able to go faster. as any one heard of 455 gears or 495 gears?? thanks