Andrewtech is you best bet.
I would just do all the gears and output shaft at once. I have seen guy do 1 and 2, start to bang geras and 3 lets loose. My buddy a full PPG set up and cheaped out on the output shaft, threes later the tranny was out again.
The thing is you need to know how to drive these cars. I have seen the stock tranny handle a 500whp track car for a long time. I run 285whp and my tranny is still in fine shape and will most likely stay this way. Drag racing is the haedest thing on the tranny and other parts, so if this is what you are doing,spend once or save until you can.
PS after you get the tranny upgrade start to save for axels.