I have found the easiest way to charge a positive ground vehicle is to disconnect the cables at the battery and connect the charger as normal. Gives you a good reason to clean the terminals before reconnecting them.

BTW, Chevy did not use positive ground from the late 40s forward. GMC did use positive ground during the AD time frame.

Martin
'62 Chevy C-10 Stepside Shortbed (Restomod in progress)
'47 Chevy 3100 5 Window (long term project)
‘65 Chevy Biscayne (Emily)
‘39 Dodge Business Coupe (Clarence)
“I fought the law and the law won" now I are a retired one!
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USAF 1965-1969 Weather Observation Tech (I got paid to look at the clouds)