76 d 100. after owning for just about a year now truck has developed a new prob. will start in mornimg with choke 1st turn of key and run fine.after i tap gas pedal and choke back open truck wants to shut off and is very hard to restart. once restarted i can keep it running by keeping on the gas when stopped but when moving it will stay running? thanks in advance for any help

Check for intake leak and make sure the carb didn't loosen-up on the intake.

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^^^ Agreed.. this is a good candidate for a vacuum leak anywhere around the instake manifold or carb. I would go and get a vacuum guage and connect to the manifold and check that. (typically around 18" or so; check with the choke on and the car running OK) If the vacuum is OK at idle then it is likely a plugged up idle circuit in the carb; I would adjust the idle mixture screw out and see if that helps. Let us know what you find, for deciding the next steps.

thanks for your replies. 3 screws that go in carb( holley1945) from bottom were loose!! tightened them back up, was able to get the truck to run and idle! so drove and seemed fine. although everytime i stopped idle was rougher and drove rougher ,eventually was unable to idle without foot on gas. am going to mess with it more tomorrow