On my last fox I replaced all the O-rings, put the R12 to 134a adapters on the connectors and had it vacuumed and filled with 134. Worked fine.
2000 Mustang GT Steeda #0048 34k miles. 99 Cobra 4V swapped, FTBR IRS swapped, exhaust, tuned by James Gordon.
Just because I give you advice, doesn't mean I know more than you. Its just means I've done more stupid ****.