overdrive?
 

Im looking into getting the gear vendors 3 speed overdrive for my th350. does anyone have this in their car now? im hoping to better gas mileage. my other option is finding a five or six speed. any suggestions?

I have a GV in my 69. I love it and highly recommned it. With a tight converter you will get about a 500 to 600 rpm drop.

well there is always the option of installing a 700r4 or 4l60e, they can be built to handle whatever a th350 can handle, and have both overdrive (which will bennefit your mileage greatly) and lockup... also with the 60e you can install a paddleshifter and shift manually aswell as enjoy automatic shifts...