I am getting ready to modify my AC system from R12 to R134 on a 1977 Dodge B300 van (with 360 V8 engine). Aside from the usual flush, and change out of the receiver/drier and O-rings is it necessary to change out the expansion valve and pressure switch? If so does any one have a part number for these? In addition, I would like to change out my refrig hoses but can’t find them anywhere. I may have to have new ones made up using the old fittings. However, I noticed that the AC hoses have “mufflers” installed inline. Are these “mufflers” designed to reduce the pulsations coming from the reciprocating compressor? Can I eliminate them without harm to the system? If they are required where can I get them if mine turn out to be rusty? Any help on my questions would be greatly appreciated.