Setting up a Duster
As others have said, swap the carb first...but honestly, I don't see this thing getting into the low 12's without some more work. The 383's are lacking in cubes to provide the extra low end grunt, but carry all the weight of a big block...not saying you can't run 12's or better with it, but it will take a lot of work.
After you get the carb thing sorted out, putting some sticky tires on it would be my next step, as far as bang for the buck ET chasing goes (Hoosier QTP, drag radials, slicks, etc).