Heads are the biggest HP maker you can throw on any 302. Even with a stock cam intake and that 650 carb it will add more power than almost any other individual mod, its just the price tag that holds most people back.
You could easily add 40-50hp with a decent set of heads alone, and without investing in almost anything else. Heads are great because they only flow what you supply them with, so if you stay mild on the intake and exhaust then the heads will only flow the maximum that both systems can create, and it sets the stage for future mods that will only complement and go from mild to wild in no time. With a stock cam and mild carb and just headers there should be no drawbacks whatsoever, vacum should remain plentiful and you should not lose any compression or sacrafice low or high end power if the heads you choose are conservative size on chambers and valve sizes.
95' GT. GT40X 64cc heads. XE264HR with 1.7RR. AODE built to 98+ 4R70W specs and PI 3500 stall. 4.10 gears. Bama tune.