Have you tried testing the coolant temp sensor to see if it's reading accurately? Essentially, you remove it and heat up some water on the stove to a certain temperature. Then you immerse the wet part of the sensor and check its resistance. After that, you bring the temp up on the stove, repeat, bring the temp up some more, repeat. It's all detailed out in the FSM. Verify temp with a digital thermometer...they can be gotten for a couple of bucks in the kitchen supplies section at Wal-Mart.
Have you done anything with the fan shrouds recently (assuming your truck had A/C to begin with)?
Have you leaned-out your carb (doing so will increase temp)?
Have you done anything which could have any obstructing effect on the airflow to the front of the fan? Things like new bumper, winch, grill changes.
Do a fan clutch test. Easy to do. Start motor with it completely cold, then with you standing outside the truck, the hood up, and you able to watch the fan, shut the motor off before it warms up at all (in other words, right away). Verify the fan stops spinning immediately. With the engine cold, if it spins longer than the engine does when the engine is shut down, your fan clutch is worn.
Check to see if your oil level or coolant level is rising or reducing. If so, could be a sign of head gasket failure. Check to verify you don't have any coolant leaks (pin-holes, water pump not weeping, coolant sensors not seeping). If no leaks, and if coolant loss is occurring, go through checks for head gasket (sweet smell from exhaust, compression check, fluid visible in cylinders, frothy appearance of oil).
While you flushed it, did you get any chunks of gunky stuff coming out? If so, may want to have it professionally power-flushed. The down side is that doing a power-flush could push a water pump closer to internal failure if it's getting close, but that's not a likely outcome in my experience (then again, might be good to know now rather than later). The upside is that if you have any gunky build-up (which your rad-flush didn't remove and could be clogging somewhere) a power-flush should rid you of it.
While removing the t-stat will allow it to run cooler longer during a given engine running session, that won't prevent an overheat situation if something else is wrong.
