I had an 86 Iroc, I miss it SO much not quite as much as the miata, but close, I got mine down to the low 13's with a stock bottom end an no bottle, that said, it took ALOT of work, heads we're gone through. Port and polish < the guy that worked my heads for me was a friend of my auto shop teacher who worked on his roundy round cars> heads were shaved WAY down as in we had to take material off the intake side so everything would mate up. Ported upper intake, aftermarket runners for the TPI set-up, don't bother with the stock ones, as they are thin, I even looked at extrude hone as a way to port them, port matched everything on the intake side so it was nice and smooth, descreened MAF, home made ram air ducts K and N filters. Trans was rebuilt then a B&M shift kit was added, along with a 2500 rpm converter, with a stock posi unit in the back, unibody connectors and a basic 4 point roll bar to help stiffen it up. Add drag launch springs to the mix and it was fairly quick in a straight line, handling at the time seemed really good, but since then I've experienced a FD rx7 and a miata with some 500lbs+ springs in it, so it doesn't seem all that great anymore. TPIS specialties supplied the cam, it was fairly mild, pulled hardest from around 2500rpm till right at 6000rpm. after that the tpi system is just to restrictive and starts killing power. Also used a TPIS "FAST Pack" that included an air foil, FPR, and other parts. Edlebrock shorty headers, y-pipe, gutted cat, and 3" flowmaster single out cat back. Superchips supplied the custom burned E-prom.
Most people that rode in it after I got done with the motor swore there was no way that it was only a 305 but, it was, made a fool out of more than one LT1 including a salesman at a dealership that swore there was no way a 3rd gen was gonna out run a 97 Z28.
On a side note with the 4 point bar, and subframe connectors, I went ahead and replaced the T-top seals, they seemed to hold with the extra stiffness.
Edit
If I remember correctly I think it was Camaro High Performance magazine or Hot Rod, but I remember someone doing a series where they took a set of vortec heads shaved them WAY down, slapped in a cam, along with, I think it was a "mini ram" intake, along with a T-56 and went out making fools of alot of people.