[Desert1957]

First of all , DON'T panic. It may be something very minor.

Do Not assume its something major with out checking some simple things.

Remember these trucks are OLD, you need to be aware of some age related problems like coolant and oil leaks.

*Refill the radiator with coolant.
*Do a visual to see if there are any leaks.
*If you find a leak, try and determine where its coming from.
*If no leaks are present , obtain a radiator pressure tested to pressure test the system
*If no leaks are present remove the tester, re-install the radiator cap and warm up the engine.
*Does it run smooth?
*Check for excess smoking from the tailpipe, let the motor warm up.

If you have NO external leaks, you need to check for other internal engine problems.

Do these steps first and let us know what you find , everyone here will help you as much as we can.

Desert

PS: Nice clean truck, looks like a great starting point for whatever you have panned.