235K is impressive for a clutch in a passenger truck, particularly one you use for towing.
The old, traditional test for the clutch is a simple one. Tested at normal operating temperpature, put the front bumper firmly against an immovable object (or have a helper to stick a foot over firmly on the brake pedal) and set the parking brake fully, then put it in 4th (not OD, just whatever is next down from OD), rev it to 3,500 or so, then slip your foot off the clutch pedal (no gradual release, immediate, full engagment). To pass the test the engine should die IMMEDIATELY. If it bogs and starts to rev back up, obviously get off the gas pedal and push the clutch pedal down, and start planning for replacement.
That said, if you're planning to keep the truck, I'd just plan to replace it anyway. It's not the toughest job you'll ever do, and then you're good for another 235K or so.
Do the works when you do it, pressure plate, clutch plate, TO bearing, pilot bushing. It just sucks to have to go in and re-do one of those later, since all the labor is the same.