If you are using the electric pump to help the mechanical pump it will be on the low pressure side . It cant hurt as long as the original fuel pressure regulator is in place . Un needed fuel is returned to the tank. As far as the heat problem , it is most likely the t stat . My wag is you have a different problem than the available fuel ( tank pick ups , tank selector valve valve ect) On the safety side , you can add the original inertia switch in line from the 99

 

Current update.... I discovered that the injector/ glow plug harness pigtails have gotten brittle and broken. I have ordered the replacement pigtails (4 for 71.95 shipped). They should be here Thursday. I am hoping that it will allow me to troubleshoot the fuel delivery issues better. This is possibly the source of all my issues.