Recommendations

In my opinion the best way to get 300-400hp in a well mannered daily driver for the car you mention is a V3 SCi blower. Aim for about 8psi. Stock heads, intake and cam will work fine. If you put the money in to a properly installed blower setup, you'll have a well mannered daily driver with some respectable power.

I'm not sure what your idea of "budget" is. If you buy new blower kit and the supporting goodies, you're looking at about 5k in cost by the time you're done. And that includes you doing most of the work.

General options. I'll assume you meant at least 300 to the wheels:
Really cheapest: Nitrous all else stock $500+ & $$$ for bottle refills.
N/A: Intake: AFR165-185/TrickFlow Twisted Wedge/11R 170 or 190 heads. Heads: Ported Performer, RPM, Systemax. Custom Cam by FTI and bolt ons. $4k+
Blower: see above advice
Turbo: B&G or Pony down kit. https://ponydown.com/ponydown/index.php?main_page=index&cPath=35. Or used HP, Hellion (non-"heat"), or incon. $4-6k. On3 has a lot of lovers because they're the cheapest. Past business practices and shoddy parts have led me to not recommend them.

Newer Hellion "heat" kit might be fine, but I don't know them. Old kits were amazing.

If you meant 300 at the crank: Explorer motor or explorer parts and bolt-ons. 260+ rwhp. $1k+ after bolt ons. or thereabouts from a junk yard.

Good luck.