What old man Tom said. The car will be lighning fast with the stock V4 RA gear in it. I did pull several 12.7 passes in a bunky Version 4 STi with over 180,000km on it, rattly engine, stock dump pipe, stock boost, rusty shuddery brakes and an old air filter. Mine was not an RA so it had the wide ratio box that is slightly faster over the 1/4 mile as you can stay in 4th gear. The RA version needs 5th even if you run 4th to 8000r/min.
Spend an excess money you have on getting the cambelt and idlers done, the radiator serviced etc while the donk is out. Enjoy it as a V4 for a while, you will not be dissapointed!!!