Today's gasoline is formulated for closed injection systems with no regard for evaporation qualities.

Back in the 60s and early 70s, gasoline was formulated to retard evaporation, since almost every car had carburetors open to the atmosphere.

So yes, today's gasoline evaporates much faster than back then.

The plus side is, when the gas evaporates, it does not leave the varnish and other crud that it used to.

The solution is to spray carb cleaner in the intake to allow the engine to start up and pump gas into the bowl. Either that or install an electric fuel pump to be used temporarily during start ups after the bowl goes dry. But don't plumb it so the mechanical pump is trying to pull gas through the electric pump - that won't work.