340, How much horsepower? 1/4 mile time?

The transmission is a a833 from a 1966 Barracuda Formula S that I parted out a few years back. (don't worry, VERY, VERY rusty!) I will be rebuilding it real soon, I will probably leave the gears alone for know, I actually don't know what 1st gear it has yet. I also have a 3.91 rear I could swap in to see what difference it makes. I bought the 4.10's because the price was good.