I have been looking for a high-zinc content motor oil that isn't a 'racing oil' at $7.50/quart.
I stumbled across a motor oil sold at Walmart - the brand is 'ACCEL' and the weight is 10W40. It's $2.50/quart and meets the SG standard, and says on the bottle 'for use in cars manufactured before 1989 that require SF/SG oils
'. I found the MSDS online and emailed the mfg. to ask about the zinc level.
The manufacturer rep told me the zinc content was 1150 ppm. This is much higher than most current oils, and I read online (FWIW) that SM rated oils have 0% zinc. In '07, some oils had around 800 ppm.
So, for us owners of ancient iron, this oil may be an inexpensive option that provides higher levels of zinc. I am running it in an old ATV that is spec'd for SF-rated oil, and will start using it in my '83 GMC plow truck.
I'll try to post pix later of the bottles, as seen at Walmart.