I have yet to do anything with my yearly bonus, but I think it's time to spiff up the old Camaro. She's a 92 RS 25th Anny addition. I'm already doing small things, like lights, new dash, seat covers, and a few other small things... but now it's time to put somthing in the engine, without buying a lt1, or an old 350... I want to keep it as original as I can... but adding some horses/torque.

What would you recommend with a $4,000 budget?

 

A supercharged 305

 

With that sort of budget I would be looking at 454s. If you really want to build up your 305 you are pretty much unlimited.
Lightweight forged crank, splayed 4bolt mains, alluminum rods, keith black blower pistons, vortech heads, and a 6-71 blower will do nicely.

 

just my opinion, and I'm a 305 guy. If you want lots of H/P, then step up to a 400 or a 383, you'll get more out of them, and do it cheaper than with the 305. For instance, you can probably get a 305 in the 13's eventually, but with a lot of mods. Even a mildly built 400 should push it into the 13's and the moter won't be nearly as high strung and undriveable as the 305.
Now, that being said, you can make a nice cruiser out of the 305 with some minor mods and still get decent mileage. What I would do is to try to make it into an L69, this can be done fairly cheaply and with headers and using all other L69 parts. If you want to go faster then put it on the bottle for about a 125 shot and call it a day.
The combo that I'm running is exactly that with a little different cam, desmogged, and a 5speed, 4.11 posi. Koni shocks,struts,swaybars, springs. Boxed the rear control arms and installed an adjustable panhard bar. I have 00 SS 17x9 10 spoke wheels with Goodyear F-1's on it. I don't think I have $4,000 in the whole car!
It's not a rocket, but it keeps the ricers at bay.