I would lean more towards a fuel delivery problem. Dirty tank, plugged feed line, bad fuel pump, clogged filter, pump to carbs line clogged. When it initially starts it’s on fuel that has seeped by the blockage and when it’s gone the engine dies. Sit awhile and a little more gas makes it to the carbs and again momentarily fires. Just an idea for some things to check.

Martin
'62 Chevy C-10 Stepside Shortbed (Restomod in progress)
'47 Chevy 3100 5 Window (long term project)
‘65 Chevy Biscayne (Emily)
‘39 Dodge Business Coupe (Clarence)
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USAF 1965-1969 Weather Observation Tech (I got paid to look at the clouds)