If you're just lookin for a number like 350 I think you're wasting your time!
Set a budget for it, talk to whoever you're gettin to map it and get the car mapped!
I've drove several cars and one that was 300 was nicer to drive than one with 330 and another with 465 was every bit as nice as the one with 300! And I don't mean nice as in great power it's how the car felt to drive!
Supporting stuff is as important also! Brakes suspension tyres etc.. Don't forget them!