The 307 in my 69 camaro (i beleive to be origonal, no vin stamp, but date codes and app codes all point it to being origona to the car)

Has 70cc heads- which should put it around 9.5 compression- If you were to stick a set of the new Iron vortech heads w/ 64cc chambers you would get the comp up to 10.1-10.5.1 and it would really wake the motor up, although you would really have to use 92 octane gas...

the 305 heads are 58cc- and your compression would throw your compression up around 13.1 which would suck unless you happen to have an unlimited supply of race fuel around Thats why people say to stay away from them...

Those new iron vortechs are great street heads, have all the acc brackets, and can be had brand new completly assembled for about $450... Only sucky thing about them is you need to get the vortech specific intake manifold for them, although if you are still running the origonal Cast iron one, getting a new aluminum one would be a good step anyway.

If it were me(and it kinda is, since i will be doing the same thing with my 307 next spring ) I would tear it apart, make sure the bottom end is solid (maybe get ARP main studs installed while its apart for inspection) Do a stock rebuild on it- and put in a mild cam like a comp xe258 or xe262, put on a 4bbl, and run it. Should be good for about 250-275hp which is pretty good for a 210hp stock rated motor.

Thats my thoughts anyway, hope this helps!
Ben