You could try pinching the affected tubes shut...it isn't a perfect fix, and it'll have a negative effect on your cooling, but it should get you home. You might couple that with "sealing" the tubes with some RTV or something, and then leave the pressure cap loose on the radiator so the system doesn't build pressure, then don't work the truck too hard and keep a close eye on your water temp.
Hope that helps some...good luck!