See that little disc at the bottom of the cap with this small rubber gasket? That's the poppet valve. That is a modern reservoir style cap. It will work.
And you'll know right away whether it's working or not. Install it with the radiator filled to the top. After you drive the truck around and the engine heats up you'll notice the reservoir tank has more coolant in it.
After the engine cools down in several hours, the reservoir tank will go back to normal. If it doesn't, well then that little caps not working
