OER Parts offers a wide selection of Battery Accessories for your 1977 GMC G25. OER Parts offers 1977 GMC G25 Battery Tender, 1977 GMC G25 Battery Managment System, 1977 GMC G25 Dual Battery System Controller Set, and 1977 GMC G25 Battery Relocation Set. Battery Mat Battery Topper Battery Terminal Protectors Battery Post Cleaning Brush Battery Terminal Puller