1965 Plymouth Barracuda Transmission or Gear Vendor?

I have a 1965 Plymouth Barracuda that I have recently restored. I put a 408 stroker in it with a 727 transmission and a 373 positive rear end. I'm looking to either change my transmission or add a gear vendor to obtain overdrive. Which would be the best option - a 4 speed automatic transmission or a gear vendor? If recommending an automatic transmission which one would you recommend?

Thanks in advance for your suggestions!

I believe the THM200-R4 has been used as a compact OD. Youll have to adapt it. The Mopar 518 tailshaft is too thick for the 65 tunnel.

And the GV is hung off the tail, making the D/S pretty short. It was a really tight fit in a 68 tunnel. I can't see it fitting in the 65 without cutting. The short D/S will make it hard to get satisfactory u-joint angles to be vibration-free.