Master Cylinder Question(s) For the experts

So, here is my M.C. setup as pulled off car. I purchased a gasket set but it only included a foam gasket. From the looks of things, there are TWO foam gaskets needed.. One against the M.C....then the plastic ridged piece that the rubber boot attaches to, then another foam gasket against the firewall...??
Also, is the round, rubber seal that seats in the M.C. available, cause I can't seem to find one.. And, is the plastic ridged piece available..?

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