I’ll throw my 2 cents in for what it’s worth. First off, if I’m reading this right you are describing two different issues.

“......See the car ran fine unless you killed it after geting it to operating temp and after that it didnt want to crank......”

If you are saying that after shutdown, the engine wouldn’t turn over then that issue is likely heat soak on the starter motor (pretty common on older chevy SBs especially in a tight engine compartment like the Monza/Vega. The cure for that problem is usually to wire in a remote starter solenoid.

The second issue, vapor lock is caused by the fuel boiling in the lines prior to reaching the carburator. While the problem is caused by heat, it is aggravated by poor quality fuels (the gas with ethanol tends to boil quicker that good old plain gas), altitude and outside temperatures.

Having an electric fuel pump at the tank to pressurize the fuel system (raising the boiling point of the fuel) often helps, but it doesn’t seem to be enough in this case.

The solution that I have found that is most effective unfortunately is also the most work. That is to run a fuel return line from as close to the carburator back to the fuel tank. You will need a fuel pressure regulator (which you probably should have anyway with the 7 PSI pump) and then run the return line back to the tank and tap in a return hole to the tank (usually thru the sending unit). The pressure regulator will lower the excessive pressure at the carburator by bleeding off fuel that is returned to the tank. In the process it will purge any vapor in the line and more importantly keep the fuel constantly circulating so it doesn’t sit in the fuel line long enough to absorb enough heat to vapor lock.

As far as fuel pump mounting as mentioned you really want the pump mounted as close to the tank as possible and ideally lower than the fuel level in the tank. All of the pumps I have dealt with will create at least some vacuum to pull fuel to the pump, however if they lose their prime it can take some time to pick fuel back up again. In those cases where I have to mount the pump in a location that is higher the fuel level I make sure that I run the fuel lines to and from the pump so they are higher that the pump (basically the pump sitting in a low place in the fuel lines. This insures that even when the engine is shut off the fuel remains in the pump instead of draining away from it and it doesn’t have to worry about picking up prime.