Welcome to the site! Great to have you here!!!
Well, here's my opinion, which may or may not be what you're looking for.
First, you've got a great looking truck!!!
Second, if you're truly interested in reliability, don't add power! Especially, don't increase rail pressure. Increasing timing will increase in-cylinder pressure and pressure rise rates and lead to increased engine wear as well.
For reliability mods, I would stick with filtering upgrades, fluids, etc.
I don't think there's much reliability increase to be had with a rail pressure gauge, but it won't hurt. I have one, but more for performance dialing than anything. A low pressure fuel gauge could be a good idea, and I like the banjo bolt approach.
Go with a good 2 micron fuel filter, and an additional water separator if you'd like. Install a bypass oil filter. Change out all fluids to a good synthetic. Install a coolant filter. Ensure that the fuel tank vent issue has been corrected. Use a quality fuel additive (Amalgamated, Stanadyne, Schaeffer's, or a B2 blend). Install a transmission cooler if you haven't already, and possibly a Mag-Hytec deep pan.
Check head bolt torque. Check valve lash. Install centramatic balancers or Balancemasters on wheels and driveshafts if so inclined. Use a quality Oil Analysis Lab at oil change intervals.
Save your money for a quality ball joint upgrade, and a free-spin hub kit that you'll likely be needing soon.
Consider the DSSS or another sector shaft brace. Investigate air filters closely. The best bet is probably to keep the factory filtering setup. Definately do not go with K&N or the highest flow filter you can find.
Since you have aftermarket wheels, make sure the spur retaining washers have been removed from the wheel studs.
Keep all hinges, latches, working mechanisms, etc oiled. Wash all winter salt/grime from the undercarriage frequently. Keep things underneath coated with paint.
On a side note, keep a close eye on the bushwacker fender flares. They are notorious for rubbing through the paint!
These are not "fun" upgrades, but they should help with the reliability aspect some!
--Eric
p. s. I'm well aware that I've not followed the above path to reliability when it comes to the "don't add power aspect" :-laf