pull the cover and change the oil on the rear axle

when you have it off,the gear ratio is stamped in the edge of the ring gear along with the date

no guessing that way

2.76 may be slow out the hole but it will fly on the highway

IMO,add HP to those gears and they will go fast...300mph dragsters use a 2.76 gear with 1400HP

so if i was just to go the 4bbl intake setup and other easy bolt ons, how much of an estimated gain will i be looking at?

http://www.summitracing.com/parts/SUM-G9040/

http://www.summitracing.com/parts/WND-8007/

http://www.summitracing.com/parts/HLY-65-1850S/

http://www.summitracing.com/parts/CCA-K20-208-2/

This is what I'd use. Maybe more cam if the gears are in the 3.23-3.55 range. That manifold should match up ok with the smaller 318 port. Probably a little bigger, but if it bothers you that much, pull the heads and enlarge the runners to the 360 intake runner size.
The four barrel will pick it up though, those two barrels suck.