RealTruck carries a great selection of custom door sills your 1975 GMC C/K Pickup 3500 truck. See the latest in door sills you need to trick out your GMC pickup. RealTruck carries stainless steel, billet aluminum, diamond plate, and illuminated door sills for your 1975 GMC C/K Pickup 3500. We also offer free, fast shipping, and the best customer service you can find. Shop now or give us a call at 877-216-5446.