Transmission chioce is up to you, PG or 400 are both excellent behind big horsepower for the strip. PG probably out numbers all of the other transmissions combined for pure drag cars with the 400 as a close second and the 400 might be slightly better for the street.
A stock converter won't hold up to a trans brake, there is just too much pressure build up and it will balloon but it sounds like you got to see that first hand. A converter designed to stall in the 3000rpm neighborhood would be a good starting place. Converters will stall at slightly higher or lower than the designed stall speed depending on horsepower etc....
You will have issues with your drive shaft length as the 400 is longer than the PG. Chances are your cross memeber may or may not need to be changed. Depending on the type of shifter you have you will more than likely have to get a new one. I run a B&M shifter that is like the Hurst Quarter stick and mine has an interchangable plate that can work with 400 or a PG.
Anyway there is my .02 cents.