Here are the cliff notes..
SVT 2.5L 200 HP stock can be prepped to about 220 HP or so with easy bolt ons, MAYBE 230-240 with alot of careful custom tweaking... Now with internal mods /headwork and BIG BUX, the pro drivers have gotton over 320 HP But not at all feasable cost/benefit.
3L block with 3L valve/SVT or 3L/SVT cam "hybrid" heads make about 220-270 HP depending on the specific plan you follow, bolt on only without expensive internals. One guy made about 290 HP with this combo using special race cams. This is a relatively cost effective approach if you can do the work.
The there is F.I., vortec S/C making up to 350 HP but some bugs with the S/C itself that may have been worked out. $3500? Then, the turbo is comming. I am betting when all said and done about 400+HP and (?$5000) but both of thes routes may be pushing the limits of both the internals (rods, bearings, cooling, oil systems etc) and drivetrain (tranny, dif, driveshafts)... big bux for a car without much resale potential.

But it would rock..
