I know the history of the car from about '86 on, and it didn't get much use to warrant the wear on the inside of the cap (which is wore to the bone). Could it be a '76 cap? I suppose it could. But it's curious just the same.
Tony sent me a copy of an original sales invoice, but all it mentions is "Engine Trim", and not what that consisted of. Looks like there are several Sprint owners on the site here. Would like to hear from them on what they're finding for original chrome parts.
Kevin, you mentioned that you found a chrome master cylinder cap. Were there any identifying markings on it? Mine is currently painted (rather poorly) a silver color. A little scraping reveals a finish that looks more like yellow zinc. My oil cap is not original, so I can't help any there. Valve cover is steel, painted blue. Air cleaner is chrome with no snorkel, and a date code of March '66.