GM Air was a Dealer Installed Option for Chevy trucks starting in 1958, so probably remained like that until it became a Factory Installed RPO in '65 or whenever.
I don't know about 58 but for sure in 59.
Kicking self for selling off my Taskforce trucks. Still looking for an LCF or conventional big bolt in decent shape.
As of 10-26-2022, A 55.2 Taskforce long bed now the work begins
