Intake filler/ thermostat housing combo

Hi All

Here is my situation. I am running a generic AFCO radiator in my Duster. When I installed it, I installed it a little lower than it probably should have been. As such, I have always questioned weather or not I was getting all of the air purged out of the cooling system (I have not had overheating issues). I looked into moving it up, but its design is preventing that. I know one of these intake filler necks would address my concerns.

Question is, If I add one, I would effectively be running two radiator caps. To keep them from fighting each other I thought I would need to move my standard 16 lb cap to the intake and get a higher rate cap for the radiator. Is this the right thinking or am I totally over looking something simple.
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