OER Parts offers a wide selection of Cruise Control Components for your 1977 GMC C25. OER Parts offers 1977 GMC C25 Dash Mounted Switch Cruise Control Unit For Use with Non-Computerized Engines, 1977 GMC C25 Dash Mounted Switch Cruise Control Unit For Use with Computerized Engines, 1977 GMC C25 Column Mounted Cruise Control Unit For Use with Computerized Engines, 1977 GMC C25 Column Mounted Control Cruise Control Unit For Use with Non-Computerized Engines, and 1977 GMC C25 Universal Cruise Control Handle.