I suspect your issue may be with the fuel pump bleeding back to the tank.
Ok, so the fuel inlet in the carb is on the top of the float bowl, where the needle and seat reguilate the flow. Certainly, for a while, the fuel filter will be pressurized, but probably not for very long (never have measured it, but probably maybe about 15 minutes, with no pressure by the 30 minute mark?), so that fuel pressure will probably migrate back to the tank, but not siphon fuel from teh float bowl, I suspect. Still, unless it has evaporated, there should be some residual fuel in the fuel lines and filter to the carb.
As the fuel pump usually is at the lowest point in the fuel line system, fuel in the tank should keep the fuel lines filled and ready for action.
So, perhaps some diagnostics need to be done.
1) After letting the car sit as normal (a day or more), not started or driven, unhook the fuel pump feed rubber line and see if fuel runs out. Of the rubber line itself and/or the fuel pump. Recover the fuel from the fuel pump to see how much volume is there.
2) Then unhook the fuel pump output line to the fuel filter and carb. See how much fuel runs out of that line as to volume.
3) Operate the carb accel pump to investigate how much fuel is squirted from the accel pump squirter on the first pump. Then the second pump. IF any air comes out, too.
4) Now that the presence, or lack thereof, and amount of fuel at each of those locations, put everything back together securely, put the carb on the top step of the fast idle cam (would need to remove the air cleaner and manually close the choke plate fully with the throttle opened a bit in our warmer weather).
5) Check the engine oil level on the dipstick and smell the oil to see if it might smell of fuel
6) With the trans in "P", start the car, paying attention to crank time in seconds. This will indicate how long it might take for it to start with dry pump-to-carb fuel lines. Record this time. Once the engine starts, jab the accel pedal to allow for normal fast idle speed. Then you can drive the car as you normally do. Once driven for about 20 miles, park it as normal.
7) Next time you drive the car (a day or so later), using 30-40% accel pedal position, record how many seconds it takes to start and run. Hopefully, this time will be less that the test with the dry carb fuel lines.
Two side issues, make sure you have the correct type of gas cap on the car. How old are the fuel line rubber sections at the tank, at the rear of the stub frame, the section going to the fuel pump, and on both sides of the fuel filter. Ethanol'd fuel dries out the rubber from the inside of the hose outward, until the outer rubber layer will drop off revealing the fabric reinforcement layer of the fuel line.
The 7 steps might seem a bit hokey, but until you troubleshoot and see what's there, you might not fully realize what might need to be done and to what. OR speculation can run wild with all sorts of "fixes" offered up.
Hope this might help with diagnosis,
CBODY67