Personaly I'm going with the ej22t on my stock 98 DOHC heads, basicly NO wiring
the sti shortblock, even though semi closed deck, is still VERRY open. The cylinder walls are verry thin compared to the ej22t. If you someday want to upgrade past 400HP, then I would stay away from the ej257.
as far as heads go, duel overhead cams are always better than single. But if you have the SOHC mounted up on the car already then it would be pretty much plug and play. in the end it all comes down to how much total power you are looking for and just how involved you want to become in your project.