i just rebuilt the carb now it runs worse

Those year slant sixes were known for having heat soak problems as well as bad floats. You probably have a combination of problems. You did check and set the timing right? All the emission equipment still intact and functioning? If not, you just found part of your problem. EGR is very important to an emission calibrated engine as it keeps combustion chamber temperature down. This could be causing your dieseling problem when you shut it off. Along with crappy fuel or too low of octane. There's a lot of things that will contribute to your problems so you'll need to take them one by one.

I would first replace the floats with new ones and set them so the top of the float is even with the top edge of the carb bowl. Next you need to make sure the power valve is free and not sticking. Then I would probably drill the jet to the next drill size from what it is, be really careful here but these carbs were set up so lean they were beyond borderline. Reset you timing and drive the car. If it spark knocks retard the timing a few degrees at a time until it stops. Don't go past 0. You may be able to go as high as 16 though, all depending. Then turn the idle speed down as low as it will go and turn the mixture screw out a little to fatten it up. This should stop the dieseling. Good luck.