www.50resto.com
great source of restoration parts, and they have corbeau seats too. new carpets and trim, billet and CF parts, etc. if i actually had money i'd have so much stuff from there...
as far as horsepower, stick an intake on it. i like the Trick flow. full exhaust too, meaning o/r midpipe, high-flow mufflers, and long-tube headers.
i'd give it a shifter too, help save the trans. not sure how much a stock clutch will hold for that year, but might wanna consider a Spec stage 2.
of course, you could always get a little horsepower in a bottle!