I've got a firebird with a 305 in it right now, and I have a 305 out of a Z28 HO of the same year (1984) sitting in my garage. What kind of power can I get out of the 305? I only have it so I can rebuild it and swap it with the one currently in my Firebird. I looked and apparently the 84 Z28 HO only puts out 190 HP. I figure if I'm going to rebuild an engine, I only want to do it once, so I want some good power.

I was wanting somewhere in the 300's for horsepower, the more the better. I know I'll need a better transmission so don't tell me that. I dont' have THAT much experience working on an engine but want to do this as kind of a project/learning/fun thing.

Is it possible to get more HP out of the engine with the current (stock) heads? or do those need to be swapped out with better ones? Is there a kit anywhere that will basically get me everything I need to build up this engine? I'm just trying to do all my research right now...

Head porting. Machined for 1.94" intake valves. More cam. Headers and good flowing exhaust all the way back.

100 HP gain is reasonable with modifications such as these.

Personally, I chose World heads, but they still need to be ported. 250 RWHP estimated was the result. Now going with a 350 shortblock, though. Much easier to get that kind of power.

Is it going to be a strip car or a street car?
I've done a couple 305's and have seen almost 300 at the rear wheels.
But in a budget, it's cheaper to do a 350. parts are more readily available.
If it's a street car I would concentrate on TORQUE rather than HP....

Torque is what moves a car, horsepower is what sells them....

You can follow my mods in the sig to get a nice 300 hp or so dfrom a 305. It runs extremely well, too. Porting and polishing your HO heads will give you a good 30 extra hp. Follow the link at the end of my sig. And call for help anytime. Folks around here are top quality and like to help

Improve breathing, improve the cam, and get a good exhaust system on it. While you're at it, you might have the heads shaved to raise compression a bit.