[Old65C10]

So, I think I need to spend a little more time playing with it before I totally condemn the engine.
I replaced the head and the T-Stat. The Radiator cap is not new, but I replaced it several years ago, but then never ran the truck. So, it is a few years old, but not really used.
I pulled the water pump and it is good. I will flush out the engine before I put it back.
The long story is this: in 2017 I found this truck behind a barn near Yakima Washington. Last on the road in 1995. I pulled it out, did all the normal stuff to get it running, new brakes, tires, fluids, etc.
I drove it a little on short runs to the store, etc. and it seemed OK. However anything more than 10 miles and it would overheat.
I assumed back then that the head gasket was shot and that was why it was left behind the barn. I ordered a new complete gasket set and it sat in the box in the shed with the truck just parked until last week.
Now I need the truck for my son, he blew the trans in his car and we need this for him to drive.
I pulled the head, replaced the head gasket, replaced the T-Stat, pulled the water pump, etc. I started it up added water and let it idle. It overheated in a very short time. I then let it cool a bit, added some more water and let it run. I keep adding water to keep it topped up, but then it overheats and spews it all out.
It has never had a fan shroud that I can see. It should be able to idle for a long period of time with out overheating.
I do have a replacement engine, but it is "assumed good", not proven good.
I may try to fill it up one more time and see what happens, but not sure it is going to be any different than the last time.