[Toivo]

the cooling system needs to be pressurized entirely, including catch cans. The catch can not only "catches" the overflow, but should return it to the system as things cool down. It can only do this if it is part of the overall pressurized system. I would expect the second Port to go to the radiator. The tank is needed on Cobras due to the usual fact that the radiator top is lower than the manifold and a "high" point is needed to fill things up.

Just my understanding of how things work.