Pontiac firebird replacement engine?

[KirsRigz]

What is the best engine i can put into a 1999 stock v6 3.8L firebird with the fewest modifications? I don't want to buy a whole new car cuz i've already put a few visual mods on the body, so i want to drop a new engine in it....

 

[Zimgxp]

3.8L v6. You could do a v8, but it would involve wiring and computer change.