Reviving a 44yo ac system tips ???

My Scamp is a 1971 with factory, not dealer installed AC, I rebuilt the compressor with new gaskets and PAG100 oil. I have a new dryer not installed yet. When I took the compressor out it had a little bit off pressure in it still. I have a new vacuum switch for the dash controls. What kind of oring seals are the best to use and where to get them? Also I plan on replacing the expansion valve as the little copper tube broke as I was moving it. The fan works. Any thoughts on if I'm missing something or procedures I need to follow? Also the lines I plan on having the rubber redone at the hydraulic shop but what are the little muffler things? Do they have anything in them that goes bad or are they just for sound suppression? Sorry so long, any input is appreciated, thanks.