I did a search on production numbers and this thread came up. Your '65 Chevy C10 with a factory 292 six cylinder and factory A/C, is, in fact, a very rare combination. The factory A/C brackets, as well as, the factory power-assist steering components for the six cylinder engines are very rare and difficult to locate in good, used condition.
At one point, I had a link to a website with factory production numbers on 4-5-6 Chevy light-duty trucks, but I tried it today and it is no longer functioning. I will continue trying to find it and, if I do, I will post it.