K20 (4x4) — 1971–1986. K20 Suburban — 1971–1986. Booster Conversion Kits. Disc Brake Kits. Front Wheel Service Disc Brake Kit, 1971–1986 Chevy 3/4-Ton & 1-Ton 4x4. Transform the braking performance of your classic GM truck with thiscomplete front and rear Wheel Service Disc Brake Conversion, engineered specifically for1971–1986 Chevy ¾-ton and 1-ton 4x4 trucks.