What is the best way to get an overdrive auto in a 67 Barracuda?

That's a ton of info, going to have to examine that closer after work tomorrow, my next question was answered, the weight difference which is signifigant. I need at least a 2800 rpm stall, I'm running a 440 with a 727 and 355 gears, I ran a 12.40 in the quarter blowing the nitto drag radials off at the line and with some bad high rpm breakup issues, car was going through the finish line at 6700. Cruising down the road it's around 3600 at 55 mph. Very uncomfortable. I appreciate the information.