Transmission ?? T-5,C4,C6

[bosss50]

I am trying to decide which transmission to go with, my car already has a t-5 in it(87 GT). But after I get the engine all sorted out I will be making alot more ph & tq then the t-5 can handle. Plus I am tired of the stick. Which tranny would be best to handle 500+ hp on the street and the strip. next year I will swap out my 306 for a 331 so this tranny decison has to play out riight for this combo and my next.