According to the Chevy Master Parts Books the “pin” is listed as “Roller (3/8” dia. x 2-23/32 long) - GM# 594485.

Just a simple section of 3/8” round stock that rolls in the support and track. Nothing else required to hold it in place.

Not sure what you’re asking on the “securing of the carrier bracket”???

~ 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)