['68OrangeSunshine]

Besides sub standard materials being used to assemble Asian-made fuel pumps -- even good US-made NOS pumps may have compatability issues with current gas station fuel being made with additives that are corrosive with the elastic element in the diaphragm.
Replacing the mechanical fuel pump on an Old School engine is a crapshoot now.
Same thing happened to the 350 in my '71 GMC a few years ago. I don't have a working gas gauge. I rely on using a trip log and factoring my gas buys [in gallons] against miles logged.
Not a blunderproof system.
About 5:45 PM, Downtown, coming home from work, the Jimmy started sputtering and stalled, just south of an intersection. I called a friend, and I called Road Side Rescue. The friend got there first. I gave him my Shell card and an empty plastic fuel jug, and sent him off to buy some gas. Meanwhile the Rescue guy showed up. He splashed about 3 gallons into the tank. No Start. Rescue guy left. My buddy came back with about 4 gallons. We added that. still no start. Now I had to call Road Side Rescue back and request a tow. The flatbed got there about 9. I was home by 11.
When I replaced the fuel pump, it lasted about 100 miles. Then it was spraying gas all over the underside of the engine. Towed home again.
Next one lasted 90 days.
Third time was the charm.
I was lucky, my SBC block has that stop bolt, that sets up the Fuel Push Rod between the ''shoe'' on the pump and the cam lobe. Just have to remember to disengage the set up bolt for running.