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

Treblig said
The 700R4 is just like the 2004R in that it can be used without a computer if you use a non lock up torque converter. My 2004R (in my Barracuda) uses a non lock up converter so I can just drive it like a regular car and the trans makes all the shifts on its' own. Yes, I lose 1 - 2 miles per gallon because the 5th gear (converter lock up) doesn't function but it makes it so easy to drive and less electrical to hook up. The 700R4 that I have in my son's '46 Chevy also uses a non lock up converter (no computer or wiring). He drives his car everyday with no issues as well.
Treblig

Thanks for catching the non-computer function of the 700R4, Treblig. The lock-up function adds weight to the reciprocating assembly too, so for a drag only car, a guy might want to consider that.

I use a normally open switch in the 4th gear circuit along with a simple toggle switch wired with 12 Volts to engage or dis-engage the lock-up feature. This way it only will lock in 4th gear.

It is very much like having a 5th gear, as even with a highly efficient, high-stall 3600 rpm torque converter, there is still about 350 rpm drop when cruising at freeway speeds.

200R4 3 (Medium).jpg