When restoring any car, the little details count! The SMCO (Stant Manufacturing Company) radiator cap has long been accepted as the "correct" radiator cap for most all of the 65 and 66 Mustangs. I have definitely seen the SMCO cap on most all San Jose plant produced cars which, of course, include the 65 and 66 GT-350 Shelbys.
Lots of folks may not know that AC radiator caps were also used on Mustangs. Yes, AC - the brand normally associated with Chevrolets and other GM products.
I have observed a few different variations of AC radiator caps on various Mustangs, but the early Dearborn built Mustangs, usually had the RC-6 AC cap that is pictured above.
This radiator cap is now available as a very nice reproduction. If you have a 64 1/2 or fairly early 65 Mustang, particularly a Dearborn built car, this cap would be correct for your car.
It is available under our part number EG1991. It features a zinc plating like the original.