one way to figure out gear ratio, jack the rear of the car up and put it on stands ..put tranny in neutral make a mark on like the rear of the driveshaft and on part of the pumpkin so u can see where it lines up and rotate the tire 1 full rotation ...however many times the driveshaft turns is your ratio
also i wouldnt port/polish the stock heads ..i would just stick with what you have and save the money until you can afford like a used pair of aluminum heads
for basic mods just to get you goin for now until you can gather some cash ..i suggest
#1 gears and a limited slip or locker differential ...traction is a big problem and wheels like to hop ..mine did anyways so i also suggest
#2 a nice pair of traction or lift bars
i know these things dont necessarily add power but they help get what you already have to the ground which is very important ..i know everybody likes to brag about bigass hp numbers but whats that gonna do if they cant get it to the ground right?
#3 im gonna say a nice free flowing exhaust setup
go with 2 or 3 chamber flowmasters with a nice set of longtubes
and have them dump it right after the muffler ..deep sweet sound that you can hear from miles away
but thats just my opinion ..i really dont know anything