What @blacksmith37 says is true, kinda. You could stick the hose into a catch bottle, and that would tell you that coolant is coming out during high load, high temp conditions. That's it. The coolant in that bottle WILL not go back into the radiator during cool down, like in a more modern cooling system. What makes that work in a modern flow back overflow system is a dual seal radiator cap.
You could possible find parts to make that work, but in the meantime, just check the coolant level often by removing the cap in looking in the tank. Note: Get in the habit of doing this when the engine is cold. Never open a cap on a hot engine. Safety first. There are some conditions where opening the cap on a hot engine results in a dramatic coolant / steam eruption. (Normal coolant systems are pressurized between 13psi and 19psi, where water boils at up near 250 def F. If your vehicle is at 240 def F and you open the cap to atmospheric pressure, that coolant in your system will want to convert violently from liquid to steam vapor with dangerous results.)