What you have now should run 12's with ease if you can drive it out of the hole and not blow the tires off. And I have to agree with competitionwedge. Heads, cam, and some rear springs. My roadrunner, many years ago, with a real similar combination to what you have, but with more cam (Isky Z-35 solid) went 12.20's. The very next weekend I bolted on a set of edelbrock heads right out of the box. The next weekend I went 11.70's without changing anything else.
