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

I talked to a very competent trans builder a couple of days ago, he called the 200r4 a tinker toy and would likely burn up at the track if you thrashed on out on the street, basically he said they were good but not for longevity because the clutch packs, and other components are still small and aren't made of magic material, anyone have any hard miles on theirs yet to debunk this? He said a 4L80e would be a better build but not sure it would fit in the tunnel, parts are adding up fast, the Gear Vendors is starting to look real good again. It is a .78 OD I believe.