Rusty - Just a quick thought, but you are probably on target for the 8 77 being a possible date code.

I’ve got a guy I’ve known for years that runs a Firestone shop. I’ll reach out and see if he can help with the ID and get back to you. wink

~ Dan
1951 Chevy 3 window 3100
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"My Grandpa Carl's Truck and How it Became Mine"
1966 Chevelle (Wife's Hot Rod) | 2013 Chevy Silverado (Current daily driver)
US Army MSG Retired (1977-1998) | Com Fac Maint Lead Tech Retired (1998-2021)