Welcome aboard. There are many sources available regarding production numbers for the 1965, C-10 engine and driveline combinations. I would start with a Shop Manual. The 1963 Shop Manual covers most of the equipment on this platform but you must also get the 1965 Supplement. Also, I recommend getting a Factory Assembly Manual for you 1965. I purchased mine from ChevyDuty.com. They are also available on eBay, LMCtruck.com and many other sources. Best of luck with you '65.

Tony Smith
4-5-6 Chevy Trucks
501 Scott Avenue
Kansas City, KS 66105
913-207-7789
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