It looks like the fuel comes from the firewall on the driver's side of the engine, goes across the hot tins above the head and over to the (mechanical) fuel pump. It then goes back across the hot head tin and up to the regulator, then to a "T" at the driver's side carb and continues across the back of the engine to the passenger side carb.
So I see two or three places where the fuel hose is sitting on something very hot. When the engine is up to temp (hot) and then shut down and sits, everything heat soaks from engine heat and the fuel in the rubber gas hose percolates from the heat and gets bubbles in it. When you then try to start the engine, it first has to get all of those bubbles out of the line, followed by new fuel and that takes a few seconds of cranking and THAT is why it is hard to start when hot.
There are two fixes; (1.) easy/maybe effective and (2.) harder/much more effective
- insulate your rubber gas hoses from heat soak by getting them up off the head tins and engine case where-ever possible. This will make it harder for the liquid gasoline to percolate and make bubbles. This, alone may cure it, but if it doesn't clear it up, then;
- Abandon the mechanical fuel pump and install an electric, rotary, "pusher" fuel pump and gas filter in the front of the car right under the fuel tank (there is even a convenient shelf to mount it on). Wire it in to your ignition circuit so it starts pumping with key on. Using that means that the pump will push the air bubbles out to the carbs and get liquid gas to the carbs in a couple of seconds after "key on" and the engine will start much easier.
Here's a popular pump from CB Performance:
https://www.cbperformance.com/product-p/3193.htm