Hey Scottie, does the coolant level in the overflow tank go up when the truck is hot? Did you check the overflow tank lid passages are clear? What about where the overflow tank tube attaches to the rad neck, clear?

I would change the hoses next like Richard suggested.

'97 Montero 'LSR' - 4.6 gears & factory rear locker, 33" Procomp muds on 15x8 steelies, 50mm coil spacers, T-bar crank, Airlift, sans rear sway, 50mm rear frame & fuel tank lift, Aisins, ARB front bumper + 10k lb winch, 50mm DIY body lift, rock sliders, cut rear quarter panels...