Heads or gears. Unless your very mechanical I'd suggest paying someone else to do the gears... obviously you can handle the heads. I have 3.73 and am pretty happy with them, 4.11 will also work if you don't do much hiway driving.
Consider gears as a mathmatical equation, affecting the leverage your car has (actually your engine). If you change from 2.72 to 3.73 you get a 37% increase in torque. 250 ft/lb + 37% = 342 ft/lb or torque. Not bad. You also get a 37% increaes in RPM at any given speed. Thats what overdrive is for, right? I'm not sure what the stock ratio or TQ is so these # might be a bit off. In my opinion gears are the biggest improvement you can make to a near stock vehicle. After gears all your other mods make just that much more improvement (say, 37%?)
Edit..
Oh yeah... check out weight reduction. Theres a ratio, I think it's like 7# rotating mass = 1hp (tires, rims, flywheel etc) and maybe 15# static = 1hp ( spare tire, hood, seats, interior etc). Those are #'s I'm trying to recall from years ago building snowmachines and I've allready had a few to drink so check somewhere if you want specifics. Some static weight savings is free, a good place to start. Not as significant in a car but on a sled a great place to start is getting in shape and loosing the beer belly!