The one thing that you haven't really considered here is the gear ratios of the transmission. The automatic LS transmission has the crappiest (and by crappiest, I mean the longest and most gas-mileage conscious gear ratios out of the whole B-series bunch). So with that in mind, I don't see any point in trying to an LS/VTEC here. VTEC is a high-RPM deal. If your transmission takes forever to get to the high RPMs, then forget it.
Boost is the best option here. Or hell, if she just needs a little more torque for those hills then just drop a B20Z in there...