318 Can't keep fuel in filter, stalls when hot.

You can verify that your fuel pump is pumping enough volume by having the output line send fuel into a container, but you might need to rig something up to keep fuel going into the carb to have it run long enough.

Warm the car up a bit and then disconnect the high pressure line and attach a hose that dumps into a container. run the motor for 15 seconds( if it will do so). That might be long enough to determine the volume is sufficient.

Install a 3 nipple fuel filter and run a return line to the tank. It will allow the fuel to circulate a bit more and help bleed off the sir pockets. Be sure to point the 3rd nipple upwards.

Insulate and/or relocate any fuel line that is near a heat source, especially to and from the fuel pump and carb.

Verify that you have adequate fuel tank venting with your fuel cap by blowing low pressure air into the currently plugged tank vent.

As mentioned above, add a phenolic spacer to keep heat out of the carb. If you live in a relatively warm area, pull the manifold and block the heat crossover as a last resort. I haven't run one here in California for decades. I wouldn't do this in some other states that get too cold.