1992 GMC 2500 6.5 Turbo Diesel surging and stalling

New to the diesel life. Few symptoms here. Lemme explain.
Got a 92 2500 6.5 TD from my late grandfather. It sat for a year and now im discovering it's issues. Anyways, bout three weeks ago it started to surge at idle after startup. While warming up, it intermittently will surge and the engine will shake. It does this through the high idle cycle and then stops as though the high idle quit.
While driving; sometimes, especially when cold or near a quarter tank of fuel, the engine will surge and the rpms will jump about 500 rpm with noticeable acceleration. Other times, I can dump the gas pedal with literally no go. Let off the pedal fully and then try again and itll accelerate slowly.
Also, once per day, usually within the first 20km of driving, the engine will fully die with no warning. No chug, no surge, no anything. Just poof, off. Its like someone tirns the ignition off. All lights stay normal, no check engine light. Shift er into neutral and itll turn over on the second try. Then it doesn't happen all day.
Seems like its a fuel issue. I changed the filter a week ago and it got a tad bit better.
However, being that it's a '92, it doesn't have a PMD. So im assuming the Lift Pump needs to be replaced, but wondering if anyone has any ideas?