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My '75 only had lap belts from the factory, and it has Silverado trim (the highest level that year). Shoulder belts may have been an option.The threaded holes were there in the door frame for shoulder belts, but I had to take off the trim and drill it out so I could access the hole. However, the lower part of the aftermarket combination lap/shoulder belts is not exactly the same length as factory belts, so they don't really fit the way I want. Bruce