Hotchkis 30390 Trailing Arms, Rear Anti Squat Bracket System, 63-72 C-10 C-10 - Manual (Page 3)

Use another jack to support the front ends of the trailing arms.
3
Remove Original Front Trailing Arm Mounts
Unfasten the large ¾” bolts holding the front ends of the trailing arms. Lower the
jack supporting the trailing arms and they should slide down from the bracket
mounts.
Each mount is secured with 6 factory rivets. Use an air chisel to remove the rivet
heads. Once the heads are removed, you can punch the rest of the rivet out and
remove the original bracket from the truck.