I've never bought a transmission before...

Pulling out the 273 from my 69 dart and dropping in a 440 pushing about 400 - 500hp. I've been looking at TCI but I dont know a whole lot and I'm nervous to commit.
This car will be a weekend cruiser with the occasional summer drag.
With so many options out there it gets confusing for a first buyer.
I'm asking for transmission and torque converter advice and guidance please