I was kinda making a joke, unless I'm over looking something, you are right about the gears, but the hp and the speed don't match. 350- 400 hp will go 120 mph in the 1/4 mile, @6000 rpm's with a 4:10 gear, so all I was saying is if I had 700 hp and only running 120 mph id be probably looking a new driver. here is a few cal., see if they help. i dont believe the example you gave could ever happen. the idea is getting the right gear for the rpm range of you cam. you get the max. hp out of your motor the mph will fall in place.

"As an example a 71 nova with 700hp, 6500rpm chip, 350 trans, 4.11 gear and 28 inch tire. At the quarter he is at 6500 rpm. People (that don't know) say he needs some 4.56 gears, but that would slow him from 132mph (or so) to around 119 mph. But i don't think it will be any faster would it?"
http://home.tampabay.rr.com/1bking/c....htm#calc_disp

http://www.richmondgear.com/101032.html