Side oiler,
From 1958 on, all birds had a/c. May have been called std equip then. I have never witnessed a bird without?
I think

that it was Lincoln around 52ish ? that had factory air.
They were easy to spot, as they had these awful looking huge R-L clear ducts in the back window.
My grandfather bought a 1964 Ford that was loaded. The a/c was under dash factory. >>> same looking ford unit was later used for 65-66 mustang to my best knowledge.
1967 appears to be the 1st Mustang with factory air?
That brings to mind, was there a check box for under dash optional air in 1965-1966 Mustang ?
I think that 1965 was the first year for true in dash a/c for most Ford brands?
My aunt purchased a new 1964 Mercury with the electric roll down back window. I have tried to visualize the car for a/c, as I am sure if she could have ordered it, she would have.
Granted, as all through auto history, I believe that Ford Lincoln or Mercury had special concepts made that factory exec's drove with A/C.
I truly am not sure of what manufacturer in the world, first had a/c in a car?
Respectfully,
John