[kglowacky]

looking at your hand drawn diagram. I don't know much about vintage air BUT you show a crossover pipe and a shut off valve that then results in the heater hose flowing thru your overflow tank. If you have it set up this way then i think you need a pressure tank. I think you can get rid of the tee and let it flow back into the engine. My set up doesn't have but a heater hose in and one out no shut off or tees. I think vintage air is doing this because they want the hot antifreeze not to run through the heater core while the ac is cooling. I am in the process of completing my ac system using original parts so I may end up doing what you did if the coolant is stopping me from getting cold a/c.