I currently have a TH400, and w/4:10 gears it's just no fun going down the highway. I would like to swap to a overdrive transmission. What is the best transmission to look at that would be more or less a direct swap out? I really dont want to have to add any electronics if I can help it. Also what manufacturer/builder do you recommend. My nova has a Big Block w/approx 500hp. Thanks for the help.