HELP with transmission ?

[N242MUCH]

i have a 67-72 truck that use to be standard but now is auto same rear end. what was the seer of the gears in a standard rear end was it 3 seer or 4 seer. i want to go from 372 to 342 gears in the rear end. thanks scott

[69 longhorn]

3.73 was pretty common in a stick shift truck, & is a 4 series carrier(3.73,4.10,4.56 ect). The 3.42 gears run on a 3 series carrier.IMO, thats not a big swap from 3.73 to 3.42......you can play with tire sizes to make up the difference. If you go 1- 1 1/2" taller on the tire , you gearing will be fairly close to the 3.42 that you are looking for. Try this calculator to get you right on , where you need to be http://www.smokemup.com/auto_math/index.php Maybe a tire swap is not the way to go.....just another option. Best of luck,crazyL