1984 Chevy Truck Wont start

I have a 1984 Pace Arrow Motorhome with a gasoline
Chevy 454 V8 engine, it won't start. I poured gasoline in carburetor and it fires and turns over but will not continue to run. I wondered if it might be
the fuel pump, bad gas, or carb problem, or just what might cause the problem. I did have it running
a few days ago, drove it for a test drive, returned home with it, kept it running (idled low like it was going to stall out) put weight on gas pedal to idle it up a bit) after a few minutes it stalled on own, repeated attempts to start it failed, batteries are ok.

Thanks for any help!