I dont know your emissions laws there. Are you sure first off that it does fall under 'legal'? In cali, you can't turbo a car unless its been approved by the BAR or it's a carb exempt turbo kit which there's only a few of.
Very nice that your block is sleaved already. Do you know if you have forged pistons? Any info you can provide about the pistons and rods. Stock pistons probably can't handle that much all day long without a really nice tune, but forged should be able to take more than that. I don't have any experiance with your setup but Id speculate 10psi would put you over your 300whp goal.
I still wouldnt buy a kit. Piece together your own. You'll get better results. It's not hard.
edits.
out here in indiana some county's you wouldnt be able to do turbo, period. then some other county's dont care at all and never look at or emissions test your car at all.
and if you know your compression level too, that's always helpful.