Getting fast without being charged

I have a 2000 Saleen S281 that isnt the supercharged model, it has 285-290 hp depending on who you ask. It already has a performance air filter, exhaust, a saleen s belt, and has the saleen powerflash. I was wondering if there was any way i could get it to somewhere in the 330-350 hp range without any power adders like a blower or nitrous. Ive looked on Steeda and Marcymotorsport website and they have only limited info on the subject.
Can anyone point me in the right direction of some package thats offered, like heads or a new intake system that I could get that power and still come out a little under the price of a supercharger?

350 HP naturally aspirated from a 2V does not come out to less than the price of a supercharger, period.

The crappy part about the Saleen is that they only have the 2V motor. It's to bad really. If Saleen used the 4V motor then the car probably already would put out 350hp.

Saleen used to do Cobra's too, but you had to buy the Cobra and take it too them. Pricey. I've only ever seen ONE car like this.

Ported heads, full exhaust and a mild cam should get you close to that. At least that's what Sean Hyland claims on the book about modular engines. Patriot Performance has some nice ported 2V heads.