OER Parts offers a wide selection of Oil System & Parts for your 1975 GMC C15. OER Parts offers 1975 GMC C15 Bypass Valves, 1975 GMC C15 Dipsticks and Tubes, 1975 GMC C15 Filter Adapters, 1975 GMC C15 Oil Coolers, 1975 GMC C15 Oil Filters, 1975 GMC C15 Oil Pan Baffles, 1975 GMC C15 Oil Pans, 1975 GMC C15 Oil Pickup Tubes, 1975 GMC C15 Oil Pumps, and 1975 GMC C15 Oil Senders.