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

I've had one in my fat blu fish for 8 years and have ran it all over the place. AWESOME! Cruising down the highway at 70 with a mellow growl from the engine is sweet.

A bit loud (Clunk) when it down shifts but it definitely handles the HP and torque. Works for me and I run 3:55's with a 727 behind a 500 big block.