Overdrive Transmission for 630 HP motor

I went through the current threads, and couldn't find what I was looking for, so I wanted to post my question. This isn't actually for my '67 GT Convertible, but for my '55 Pilothouse Truck, although the info should be mostly the same. I am building a 630 HP 383 > 496 that I am putting in the '55 truck. It will be mainly used driving around town, and I would like to mate an overdrive tranny to the motor. My truck currently has a 4 speed in it, but I don't care whether after the rebuild it stays a manual transmission or automatic. My two goals for the tranny are its ability to handle 630 HP, and have overdrive capabilities so it is more streetable. I know that there are some after-market options with Tremec, and the like. I would like to see if anyone has used a high HP motor, and had a Mopar transmission that has handled the HP and been good on the highway. I would probably be remiss if I didn't mention that I do not want to cut the tunnel in the truck too much, since the cab of the truck doesn't have a crap-load of room to start with. Thanks with any information you can give.