[ByronRACE]

If you're using this tank as a recirculating catch-can, the can should be vented to atmosphere, and the fluid needs to enter and exit the can as the liquid in your cooling system expands and contracts. So, you need a siphon tube going to the bottom of the tank, or you need to connect your overflow line to the tank bottom. As the fluid expands, it'll fill the tank. As it contracts, the vacuum of the closed system will draw the fluid back in.

If you're using the can purely as overflow, then just vent it to atmosphere and pour the fluid in the top without a siphon tube. I don't recommend this. A recirculating overflow as described above is more useful.

By the way, do you need a set of manuals for your Stallion? I have a 1982 car (West Coast) and have scanned a full set of stallion/west coast manuals to PDF. If you need them, I can make them available for download. They detail everything and show the root source of the parts that comprise the car.