About how much horsepower should I be making with this mild combination?
305 Tuned Port Injection, Comp Cams (260/260 .444.444), Hooker Shortie Headers, .030 overbore on motor. What should this combination do in the 1/4 mile (1985 Iroc-Z 305 TPI automatic). What else should I do to the car to get it into the low 14's?

Need more info. If automatic, then you will need a stall converter and if 700r4 trans you will also need to have it beefed up some to get rid of that lag between 1st and 2nd gear.

I would do some head work.

i would say mid to low 15's and maybe 180 HP at the rears.

i would say some headwork (maybe new heads), appropriate torque convertor, and some suspension would help you alot. after that, i would think that mid 14's would be attainable.

100 shot and traction.

Would I be better off getting new heads or just doing some gasket matching/porting to mine? If new heads, then what kind should I get? What kind of suspension upgrades should be done also?

Assuming you have a 305TPI then you got 081 heads which are pretty good, just get them ported and polished.