HELP!! to turbo, or not to turbo....

[RoNiN240sx]

i just bought a '96 240sx about 2 months ago for a real good price, about 4000, ofcourse the price being that low comes with it's disadvantages, the car has 120k miles on it. everyone knows the US engine is crap, i want to turbo it but 120k miles is too much to put on a turbo right?
the only other option i can see is getting the sr20 swap, but i don't want to have to risk the smog factor and/or getting a fix it, it'd be a pain to have to switch everything back....ergh. for those of you who have done the switch, have you had ne problems with police and smogs, especially the Cali residents, cuz the smog regs suck here.
ne suggestions on how to make my car faster without risking blowing it up or having to swap then reswap...my ideal power would be at least 250 hp....i need ne suggestions...thanks...