What should i change to get into high 11's?
Your 2.1 60 foot time is not so great which is chassis. Front section of springs clamped? Pinion snubber? Subframe connectors?
Small blocks like gears, preferably anything 4.10:1-up.
I'll agree with others who have said to upgrade your converter, most definitely. Is it a 904 or 727? 904 is less rotating mass. A low gear set might help too.
Do you know what your car weighs? You can figure out approximately how much hp you have at the wheels (based on ET/mph) if you know your weight. Once you can ascertain that, then you can start to get an idea of how to build your combo towards your goal. You'll probably need around 400-425hp at the crank (figure 15-20% parasitic driveline loss so around 340-350 at the wheels) and weigh around 3100 lbs.
1/4 mile hp calculator.