blown cars can use 30's until around 380rwhp. i think some people have gone higher, but it's getting risky. 42's can go to 500rwhp i believe. Kidd made 663rwhp and if i remember right, he had 55's.
If you dont want to swap right away, also check out a stand-alone fuel system, such as the F.A.S.T. system. A good tune with those can boost static fuel pressure and save you a hassle down the road.
My 2000 GT's injectors are a different color than my wife's 2002 GT. Can't remember what color mine are but hers are pink. Both are 5 speeds. Did they go to a bigger injector after 2000. and if so can I get the ones she has or will the ECU not be programmed for that size??