Any factory R-134a system will have an R-134a fitting for the access ports. Look at it. If it's a 1/4" flare, it's R-12 (NOT R22 ); if it is a quick connect it's R 134a. Also the sticker on the radiator support should say what it is. Good luck. Use gauges

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The Golden Rule

1984 300SD (bought new, sold it in 1988, bought it back 13 yrs. later)