Connect the fuel pressure gauge to the fuel pressure test port on the drivers side fuel rail - it is pointed straight up and is located just to the rear of the middle (around the area where the rail gets it's fuel feed from). I recommend a long hose where you can see the gauge while in the cab - I pinch mine between the wiper and windshield with it's face oriented so that I can see/read the gauge while cranking & driving.

BTW - I had the exact same problem (dies in certain spot only) with an '89 Ramcharger. It turned out to be a fuel return line that was getting pinched but only under certain circumstances (when enough fuel vapor would build up in the plastic tank causing it to expand). The motor would idle fine but would die as soon as any load was placed on it = not enough fuel under certain conditions.

The fuel gauge on the windshield showed this perfectly.