[jgpnashville]

My 67 K15 with 305E is stock as it came from the factory, without an overflow or expansion tank for the radiator. Almost every time I drive it, I check the coolant and notice it is about 3 inches down in the radiator from the top. I top it off with coolant/water and drive. Next time, it's down about the same amount. No head gasket issues, so I can only presume that it's expanding and going out the expansion tube onto the pavement when the engine warms up.
Is this cause for concern? Should I fashion some sort of coolant overflow tank and drop the rubber overflow hose from the radiator into the tank or leave well enough alone?
Is it normal to have the coolant run about 3 inches down from the top? My truck is missing the owner's manual so I don't know what GMC had to say about the coolant, but to my modern mind, coolant 3 inches down from the filler seems a bit low. I know the water pumps move a lot of coolant through the engine and even though my truck only has the idiot TEMP light and no temp gauge, it never seems too hot and the TEMP light has never come on while driving.
Thoughts?