heater core out but need some answers.

WEll I have the heater core out but I am trying to figure a couple things out for the reassemble process. I have already ditched the ac stuff but i am now ditching the condensor piece that sits besides the heater core. I need to to replace the rubber gasket now so would I order one from the dealership for a cherokee without AC? Also what type of sealant should I use there to seal it up properly. Also the ac cannister that also holds a intake line. Is that really needed? Thanks
This is on a renix 89.

I would just get some closed cell foam and make my own pieces. Closed cell will not retain as much water.

Is that differnt than regular foam padding and were can it be bought at