[gmc684x4]

Nappa autozone brothers trucks lmc gmc pauls
Would be a few places that carry or can order it in Reese and Hopkins are two i know that make them

With some parts books you may have to say 79 c10
I rember doing that many times over the years for some parts i needed new drums for my 74 short box had to tell new parts guy at chevy well order me a set for a 79 c10
In 1989 chevy dropped the 74 part number and never added the supersed number to there listing