Exhaust hanger rubber rings are ~$2 ea. Change before your muffler drags and $$$ damage.

Tranny shifting is via vacuum, so fix that and it may shift fine. Vacuum pump rebuild kit is ~$100 if you have the later 1-tube type, ~$12 for the earlier 2-tube type. It is easy to rebuild (after you clean away all the gunk), you pop out outlet valves and replace the plastic piston ring (or rubber diaphragm in early pumps). You might even forget that an install a $50 used electric vac pump from a newish VW diesel.

AC - try actuating the clutch manually by applying 12 V via a 2" jumper wire. Remove the relay and jump terminals 30 to 87. If the inner part of the compressor turns, it is likely OK. May just be low on refrigerant.

Rust is trickier. What looks like a small surface spot may actually have rusted thru from behind and turn out much more extensive once you start picking at it. Not true with these cars here, but I saw that a lot when I lived in the east. A cheap repair is to cut to sound metal and cover the hole w/ fiberglass-epoxy then Bondo.

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1984 & 1985 CA 300D's
1964 & 65 Mopar's - Valiant, Dart, Newport
1996 & 2002 Chrysler minivans