my 2 cents worth. possibly a couple of issues together to make your problem
-fuel is draining back to the tank slowly
-fuel is evaporating in the carb from heat soak. last time the engine was running at operating temp or at least warmed up before shut down, the heat is trapped under the hood and takes time to dissipate. this heat is transferred to the carb and causes the fuel to percolate or evaporate out of the carb so the float bowl becomes near empty
if it happens again, before you push it back into the garage, remove the air filter and look down the throat of the carb when you move the throttle by hand, key off. you should see a squirt of fuel from the accel pump. if you see that squirt then there is fuel in the carb. if you don't see any squirt then the carb is empty and a fuel system test is in order.
you can quickly check for fuel in the tank and a through pathway for the fuel to travel to the carb by simply removing the fuel line at the carb, attach a length of fuel hose long enough to reach a container placed in a good spot so you can see what's going on from the fuel fill location (if you don't have a helper to watch the jug) and also so it won't get knocked over. I like to use an old windshield washer container because it is semi clear so you can see the fuel plus it has a handle so I can run the fuel line down into the open lid a bit so the fuel line is near the bottom of the jug, then bring it past the handle on the jug and just and tie it there with a cable tie, duct tape or whatever. the jug can easily be bungee corded to something that will keep it right side up and stable. then I remove the power wire from the ignition so no spark can occur while doing the test. then I remove the fuel cap and use regulated compressor air pressure, like a few pounds worth of psi, blown into the tank with a simple air blow gun, sealing the fuel fill spout against the blow gun crudely with a rag. if you have a separate fuel vent on the tank you may need to plug that off. if there is fuel in the tank you should soon see fuel in the jug. if there is not a clear path to the carb, like a stuck fuel pump valve or a plugged fuel filter, then you won't see or hear much coming out the hose into the jug. if there is insufficient fuel in the tank or the pick up tube is above the fuel level in the tank then you will just get air out the hose into the jug. you can also check along the fuel line shortly after the test to see if there are any wet marks from a leak, which can help in the drain back issue. I have seen new pumps fail due to a stuck valve (sometimes from just sitting around not being used) but then come back to life after doing this little trick which unsticks the valves. I think the old style fuel pump valves are not made to be used with the newer fuel that contains methanol etc and so they are stuck to their seats and blowing fuel through the pump forces them to open. like you mentioned, the fuel pump is basically 2 (at least) one way valves with a plunger in between them to cause a draw and a push effect so fuel shouldn't be able to drain back to the tank. that said, they are mechanical and rely on mechanical sealing efforts. a pump can't draw fuel or push fuel if the valves are stuck either open or closed. I have also seen the little fuel line come off the pick up tube inside the tank so a 3/4 full tank could run out of fuel if parked on a hill depending on the location of the pick up tube. with that said though, you mentioned you pushed it outside then it wouldn't start. it never drove itself outside but I assume it was running at some time prior to you pushing it outside. if that is the case then the carb should have had sufficient fuel in it to start the engine. but, what can happen with the carbs, especially on cast iron intake manifolds, is the fuel can evaporate out of the carb bowl from heat transferred to the carb through the intake manifold. if you smell fuel in the garage a while after you parked the truck that is the give away but they don't all leave the odor, it can depend on the intake system etc. edelbrock carbs don't have a fuel filter at their inlet, like some of us old Rochester boys are used to having, so the anti drain back valve which these old filters had is not there anymore. a simple fix would be to install an anti drain back valve inline if you think the drain back is the problem. marine equipment uses these valves and if you find the system is allowing fuel drain back this could fix the problem.
https://www.iboats.com/shop/moeller-...b-1-4-npt.html
a simple fix for the fuel boil off is a heat spacer gasket under the carb. edelbrock mentions it here
https://www.edelblog.com/tech-tips/resolving-heat-soak
if a flow and pressure test comes up negative for the fuel pump, like no problems, then the heat sink gasket/spacer and an anti drain back valve could be your answer. also ensure the fuel lines are routed away from any heat sources like headers or exhaust manifolds. I have used semiclear inline fuel filters before on vehicles with this sort of problem so I can see if there is fuel moving. some suppliers sell the clear glass ones as well. there is also a marine float inlet valve available at a lot of boat or 4x4 shops. these work better for sealing on trucks, boats etc that bounce around a lot. also, edelbrock carbs are not made for the alcohol fuels so I wonder if their fuel pumps are possibly not made for the ethanol fuels we get these days. possibly a reason for a stuck pump valve if you find that a reality.
a quick carb tune demo from edelbrock
https://www.edelblog.com/tech-tips/resolving-heat-soak
offroad inelt needles
https://www.edelbrock.com/off-road-n...ty-2-1465.html