Stock compressor,mod for 134a ?

I'm restoring the a/c system on my '73 340 Duster & thinking about converting it to 134a.Does anything need to be changed / modified / updated to the compressor when going to 134a refrigerant ? I understand that the hoses,orings & oil need to be compatible,not sure about the compressor itself.Will the compressor's crankshaft seal work with 134a?