I think you guys are misleading the original poster.
Your injector decision does not depend solely on what turbo you have. It depends on the rest of your combo, how much power you are making, and how fast the car is (depending on raceweight) too.
You can put a 70 turbo on a bone stock car. Does this mean that the car needs 83lb injectors? No.
A TA63 is a mid 10 second capable turbo. If you have a combo that will put your car in the 10's, then you need 55lb injectors at a minimum. If your car is going to run 11.80's with this turbo, then your 42.5's are ok.
If you are going to upgrade your fuel system, you might as well go right to the high-imp 65's instead of going to 50's, then 55's, then 57's, then 65's, etc. Do it once and be done.
Just my .O2