You get a tick at idle while overheating because the oil is so hot and so thin it is not protecting the engine, it is just being pumped around like water in a fish tank.
Have you priced a new engine for your truck?

 

Naysayers.

 

You'll be fine, replace the radiator and you'll be good to go.
But what I said about the oil while overheating is true, change the oil once you get the new radiator in.

 

Well, I pulled a late night wrenching session the night before my trip, replacing the radiator and PROPERLY rebuilding my front prop shaft (Thanks again Mike!), and I am happy to say that my 1500 mile round trip was uneventful. Even in DC rush hour traffic, with temps in the 90's, and the AC cranked, the Disco didn't even break a sweat. The 4wd worked flawlessly on the sand, and the truck was a joy to drive. There is still a mysterious vibration somewhere in the driveline that I will be tracking down, but all in all I am sold on the Disco. Thanks again for all the feedback on this topic, guys. Cheers!

 

I'm happy to hear all went well on your trip...on your vibration issue, check your roto-flex for cracks...if it has not been replaced, it might be time.

 

Thank you. Yes, the rotoflex is number one on my list of suspects. I will be doing the u-joint conversion soon.