Run it out onto the ground like God intended, there are too many stray dogs anyway.
Since most of us don't drive these trucks in winter, distilled water won't even hurt the dogs.
Seriously though, that would be an option for me. I never intend to operate my truck below freezing, distilled water wouldn't hurt anything running out onto the ground. I could drain the radiator when parked for winter like horseless carriage owners used to do.
There is a guy on the forum in the parts section that sells reproduction overflow tanks, you can get one out of a junkyard, get one from Jegs or Summit, or make one.
AFTER SOME REFLECTION, MY IDEA ISN'T SO GREAT. What will I do with water in the block when winter comes? Break my block I guess.
Looks like I need an overflow tank this summer after all.