A 1969 Chevy C-10 didn't specify a single battery type; the correct battery depends on the engine and options. You'll need to find the Group Size code. This is usually found on a sticker under the hood (sometimes on the battery tray itself), in the owner's manual (if you have it), or by looking at the old battery (if it's still there).
The Group Size will be a letter and number combination (e.g., Group 65, Group 24F, etc.). Once you find that code, you can easily find a replacement battery at any auto parts store. They'll have a chart to match the code to the correct battery.
