She looks good but she doesn’t run so good

[pickup]

When you drive the truck and let off the accelerator to slow down or stop for a red light it quits running. I have done everything I know of and wonder if someone out there might have a suggestion as what could be causing this and how to fix it. She cranks good and runs ok. It seems that you have to keep the idle up a little to muck but it will set there and run all day.
I restored this 1952 F-1 from scratch which included rebuilding the engine. I converted it over to 12 volt and had the carburetor rebuilt by National Carburetor in Jacksonville FL. Of course, new points, plugs and condenser.