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

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

I'm currently in the middle of my '69 Dart build with an Extreme Automatics built 200-4R, manual-shift, reverse-pattern, and lock-up converter. I'm planning on 4.30 gears.
Fun on the street and will be the same as 2.88s on the freeway with the 0.67 overdrive of the 200-4R.
And it all fits in the stock A-body tunnel.