Radiator overheating already

[Speedbumpauto]

With air temp in the 50's, that truck should have been at T stat temp and no more(180?) unless prolonged stop at a light. It's not unusual for the the overflow to puke in the first few minutes after stopping. That's when the most heat is in the rad/block and no circulation. Check it after it completely cools down and see if there's any coolant in the bottom. If there is, your're good unless it spits up the next time. If it's dry, it means boiling pressure is forcing more out than it can pull back in when it cools.(bigger container) Make sure you have a good cap(15-17#) and also, that 50-50 antifreeze mix thing is not the best for cooling. Pure water is the best so I try to run about 20-25 % for rust purposes. You don't need much in AZ unless you go to Pinetop in the winter.
Slow timing can cause heat. Not having a vac advance at cruise is the same thing unless computer controlled. Lean mixtures also cause heat, dirty air filter, etc. Make sure the engine is running well. They make a larger diameter chrome overflow tank. I had to get one AND add the hose before mine achieved a static condition. Another easy test to do is have a shop(or buy the kit) test for hydrocarbons in the radiator. They put blue liquid in a thing that looks like a turkey baster and pull air out of the radiator when it's hot and running. If it stays blue, you're OK, if it turns yellow, means you have a head gasket problem, most likely. That pressure will push coolant out every time. If all of those things fail, you need to look at a radiator with 1" or 1 1/4" tubes instead of the 1/2 to 3/4 tubes your current one probably has, and it doesn't matter if there are three rows or not. The only advantage aluminum has is the ability to make long, thin tubes with lots of surface area. It's actually not a better heat conductor. Sorry about the length of this. Hope something works.