It's a Shock Dampener assembly. Only available on GMC's of that era. I believe they have some
information on the GMC site.
Fred

Bill beat me to the response.

Last edited by rfs56trk; 12/13/2024 4:37 PM.

1956 3100 Pickup/Red/350/3sp OD/PS/Disc Brakes
1957 Bel Air Sport Coupe/Red/355/TH350/PS/Disc Brakes
2017 Silverado LT Single Cab SB/Black/5.3/6 Speed Trans
1947 Willys CJ2A w/F-Head engine