What increase am I looking at for Cast Iron Vortec Heads over the stock LG4. Any weight differences either.

I think Iwould put a Edelbrock RPM Air Gap Vortec Intake on. Is this a good intake and would it cause any hood (stock) clearance problems.

Unless you upgrade the exhaust, cam, and air cleaner, next to no improvement.

Assuming you upgrade those areas, less than if you shave the heads to 58cc chambers. But, if your dreams for the future include a "bore kit", you don't want to do that.

Hood clearance will largely be a function of air cleaner selection.

I had a performer RPM vortec intake with edelbrock 800cfm and 14x3" triangular air cleaner.. I needed a cowl hood for it to fit under... I have heard that the standard performer vortec might fit though...

Probably no real difference. The new manifold and the vortec 305 heads will probably free up 20hp. Since you probably have stock exhuast manifolds it might make the bottleneck worse and you could loose 20hp.

If the camshaft and exhaust was also upgraded you'd see a nice gain. But with the 64cc combustion chambers your gonna loose compression. Should still see a nice gain thought.

My car is far from stock heres the mods
87 Firebird V8 305
LG4, 4 Speed Automatic, 42,000 miles

AIR FUEL
Edelbrock 600 cfm Electric Choke Carb, Edelbrock Performer Intake Manifold, 14" Open Air Cleaner, KN air filter
VALVE TRAIN
Comp Cams Roller Cam 260, Comp Cams Roller Lifter, GM Aluminum 1.5 Roller Rocker Arms, New Springs and Retainers, Double Roller Timing
EXHAUST
Edelbrock Headers and Y pipe, High Flow Cat, 3"Hooker Cat Back
DRIVETRAIN TRANS
Auburn POSI 2.73 gears, BM Megashifter(rachet)
COOLING
165 thermostat, Fan on at start, New water pump
ELECTRIC
New HEI Distributor, Computer Delete
DYNO
187hp 263tq rearwheel, 226hp 316tq flywheel

What gains should I expect now with the Vortec heads and RPM Air Gap

OH ok then should have said somthing before, we just assumed it was stock or stockish.

Your probably going to gain a bit all around Like I mentioned probably between 20-30hp. I'd Persoanlly hold off on the heads and such until I had a respectable gear ratio. 2.73's are killing your performance, If I had to do it all over again my #1. mod would be drop the 2.73's and slap in 3.42's and work from there, but at the time I had a Z28 that came with 3.42's so I thought they all did. Gee, Ive got a cam, intake and a good carb and my car wont go.

i second the gears...i have a serious amount of mods on my engine and stock 2.73s and i smack myself time and time again for not getting gears first...now im out of money and hate myself for not getting gears before any other mod....

me too...me too