I installed 2" lowering/leveling shackles on a friend's all stock 1986 GMC C10 Stepside- No issue. No bed cutting, no bolt cutting.
It's just the fleetsides require notching of the bed cross-braces.
As far as taking the factory shackle/bolts out, we only need to raise (or lower) the frame...
1984 is when GM moved the headlight switch up some & moved the wiper switch up to the steering wheel turn signal lever. All Silverados were black with the brushed aluminum overlay glued on.
You will have to drill 2 holes for each sunvisor inner retainer. There is a long needle like guide that stabs thru the headliner and aligns with a smaller pinhole in the sheet metal. Then the regular sheet metal screw that holes these inner retainers in place. Remember short screws & drill bit...
Nice rig. Grandpa must be real proud that it is staying in the family. "FUEL INJECTION" is missing off the tailgate.
Welcome, from Wichita Falls, TX. 76310.