I have a 12 bolt posi with a 273 gear. ... . I want to know if I should put in a 350 turbo or a 700r . I have asked the few people hear that I trust and have gotten both ways. That I don't need a overdrive with that rearend, and that the 700r has a lower 1st gear, and I can hold the tranny in 3rd until I am on the interstate and then I can Idle at 80 mph. I just don't know which tranny to put in. I have a 400 sb with aluminum heads and a single carb. Yet I am not building a race car, just something that sounds good, has good pickup, but will run on the highway all day and not kill me at the pump. A traveling car basicly, that can cruise in town and the interstate.