Which Transmission to use?

I have a 72 Demon and installing a slightly built 73 340 in the car. I am going with an auto for sure, my knees ain't what they used to be. Which one would you use 727, 904, 500, 518 ?? This will be a street car, not planning on any strip racing. Will be running a lot of 100 mile round trips. Thanks for your input.