1989GTA

I see at least .3 tenths from the gear changes. That would put you around 13.2 with your current setup. To get to 12.4 you will have to pick up around 80 horsepower. Maybe less if you have good traction and a good launch.

big dave

As already stated, 11s are definitely possible with the right selection of parts. You don't need a huge cam nor the need for a flyweight car, just the right combination. Also, as was said, track altitude, weather conditions, and track conditions play a huge part in how well your car ultimately will run.