The fortunate thing is that the turbo set up on the stock motor is good to 275hp at the flywheel. Getting that extra 25 hp or so is not out of the realm of impossibility, and you sound like you know what your doing so here goes.
Total Seal gapless rings
150cc injectors (some Moose Misters should flow that much , PM Agnem for those ), and get 150cc/1000 strokes minimum out of the pump
A turbo that can flow 42 lbs/min of air
22 psi boost
Pressure ratio is 1.60
The stock cam lift at the valve is .380", with the timing events not exactly the best for boost. The intake valve closes too late in the cycle, not good for forced induction (fellow member spencergt66 brought that out), so getting a cam ground for your desired powerband with more lift, duration, etc. that is for turbo use will help here. Russ has a torque regrind available now that was designed for the loggers ( Russ' username: typ4 ).
The thing that needs to be done, which if you have the skill to do it, will open up the performance envelope quite a bit is to reclearance the piston to valve clearances so that the engine no longer is an interference style engine. The head's best flow numbers are north of the .380" valve lift range, and if you go thru the effort to port and polish the heads, you won't be able to take full advantage of it with the stock cam. Even unmodified heads are not being utilized completely.
