ok i have a 68 f100 4x4 with the orginal np manule trans with a 390 i want better millage what 5 spd manule trans are there that i can put in the truck and how do how much work am i talking about haveing to do thanks every one

 

A 5 speed trans won't give you much better mileage, and the expense of buying a trans and then the additional expenditures trying to make everything fit will buy a lot of gasoline. You have to remember the time frame of these trucks. Gas was cheap, as little as 26 cents a gallon, there were no shortages, no long lines, a gas war meant that prices went down not up. The trucks are shaped like bricks, aerodynamics are zero. No one gave a hoot back then about gas mileage. Bottom line, even with a 5 speed, taller gearing, and a more fuel efficent engine, you'd still only see, at best, a 2 MPG increase.