I've been kind of wondering about that mechanical fuel pump, too. I'm not a big fan of them, but then on the other hand a LOT of people are running them with no issues (even in SoCal in the heat!) so I wouldn't be the first to condemn it.
Still, if your fuel lines are well away from heat sources with no drastic high or low spots, your fuel filter is relatively new or known clear of obstructions, the lines are not kinked anywhere and everything looks OK and it still gets heat soak, then it might be percolating the fuel out of the float bowls (I mean, that's all that's left, other than the fuel pump, right?) thereby flooding the engine while sitting/soaking and making it hard to start. That can often be proved by going somewhere to force the heat soak when stopped, then floor the accelerator and hold it there and then start the engine. If it is percolated bowl syndrome it should start within 10 - 15 seconds and then probably run crummy for a minute or so until the excess fuel is blown out of the manifolds and then it'll run better. I don't know why your engine/Kadron combo would do this when others don't, but you could run a phenolic spacer under each carb to insulate it from the head heat - maybe that would help, but no guaranty there, either.
At that point, I would shotgun it and just install a Carter rotary fuel pump up front.
Also, Brent...... Once you get this all figured out I would make it a habit to add "Star Tron" gas treatment to each tank of gas to minimize the effects of the ethanol fuel. It's pretty good stuff and I've been using it in every tank (and in the gas I use in my yard tools) for years.
***EDIT*** One last thing: If you want to reduce the fuel pressure by half a pound or so, just add a second (or third) gasket under the fuel pump to shorten the stroke.