you have two "fuel" pumps, the lift pump on the passenger side of the block which is low pressure (~5 psi +/- 5 psi), and the injection pump (IP) which cranks it up way past 1500 psi high pressure.
Fuel can't flow past the fuel pump when it is off - unless you literally can't turn the truck off because of the shutoff solenoid being stuck open. The IP only feeds one injector at a time too so even if you are lined out perfectly on one injector there are too many restrictions to that (the IP uses pistons). Leaky injectors don't matter either, I doubt the return line system could support filling a fully stuck open injector because the path of least restriction would still be the fuel tank in my mind.
Either way, it would take forever if it was a possibility - not the few minutes (exaggeration) or less it takes you to start the truck.
Back on the main topic:
Two of the best upgrades in my mind are push button glow-plugs, and push button STARTER. Using a pushbutton lets you use brands other than the motorcraft BERU plugs, the Bosch plugs warm up very quickly but will burnout if you go too long, the BERU are more durable since they don't heat as aggressively. Never had any swell, but I am again running BERU right now. I've heard decent things of Wellman, never actually tried them. Avoid autolites and champions like the plague. For me its either Beru or Bosch (very popular for the VW crowd but our stone-age controllers kill them so only use them for push button setups).
For the starter If any of you have had to replace the cast pig-iron actuator in the steering column then you know what I mean! It's also handy for cranking the engine over at any time.
Also FYI Anyone afraid of these being hot and press-able without the key just has to tap into the keyed-power wire - the red wire with a green stripe, instead of going for always hot.