considering you havent dynoed the car locally yet (to my knowledge) i would see what it makes. you should be able to pump out 350whp on a stock LS head an cams an intake manifold. we have done it on a non sleeved LS motor with rods an pistons, our Turbo Dave manifold, T3/T4 turbo.

IF the motor runs good i see no need to rip it apart for a VTEC head. Get a better turbo manifold, 403 cams an springs an retainers.