What Paul said, plus when it comes to your convertor stall, that will all depend on what cam your using. I dont think your planning on turning the engine at to high an RPM for durability purposes. Best thing to do is, when you have all the componites of the engine ( pistons, crank, rods, heads, (ported im assuming) intake, carb, header size etc. Email all your parts spec to a cam grinder (Crane, Comp Cam etc.) and they will tell you what cam they thing you should be running to get the most power out of your engine. Once you have done that, then contact a torque convertor builder to see what they recomend. Usually they like to dyno the engine to mach the convertor for the amout of stall and slippage. But if you stay within the power band of the cam you should be ok.
If your going to run a C4 trans, then make sure you buy one that has been built strong to take the power the BBF will be putting out. And while racing the C4, add a catch can because they usually like to blurp out a little oil after a hard run.
Im running a 4600 stall in mine, but the power doesnt turn on untill 4800 RPM. When running a higher stall like that, its not hard to break the tires loose off the starting line if the track is not very tacky. Im running a 2 step and trans break in mine, so i can turn the RPM down before launching the car.