If you are using R-12, you will probably be making connection at the schrader valve on the compressor. Look for the one associated with the fat hose going to the firewall - that's the low side - toward the fender on my car. Yeah I would much rather connect someplace high and dry (like at the dryer) than reach way down there, but unless your system has been modified, you don't have that option.
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Art Benstein near Baltimore

It’s not the fall that kills you; it’s the sudden stop at the end.