Idiots...

You may want to pull the gas tank or at least the sending unit to see if the screen is intact at the pickup end. After several decades these screens disintegrate and all kinds of bad stuff can get sucked into the fuel pump and possibly all the way to the carb. If you've never flushed the tank it's cheap insurance or good preventative maintenance to do so on a car that old. Don't be too quick to blame the mechanic, all it takes is one little piece of dirt in the system and the engine runs poorly quite quickly.