ok this is what i got
3.73 gears,
70mph 2200
80mph 2500
90mph 2800
4.10 gears
70mph 2410
80mph 2755
90mph 3099
i did this with my automotive math book, so the numbers should be really close. i had to guess on the overdrive gear ratio though. i put in a .75 final drive and that got me where i wanted it too. pretty close anyway.
hope this helps
Dan