shifting shuts my car off
Wow there is a motor under all that stuff? LOL, Looks like a Holley 1945.
You may want to start with a valve adjustment. A guy I work with has a 225 in a 66 dart and he swore up and down that it was the carb, new carb he swore that it was the ignition, new dist, coil, cap, rotor, ect. the car was still dieing at red lights and when it was cold. I adjusted the valves and it would stay running. Then I reset the timing and adjusted the carb and it runs great.
While the valvecover is off i would rip out all that emissions junk and the AC if you don't need it and it isn't working. Then you can get a carb from a 73 or older (before emissions junk was standard) and you will have a way cleanner engine bay.
If you decide to keep the emissions stuff check each hose for any cracks or splits and replace them as needed.