At that time (late 70's), it was called Tenaya Lake walk-in campground. Was it perhaps renamed Sunset for a while later on? My 1978 Wilderness Press guide to Yosemite refers to it with the Tenaya Lake name, but I seem to recall staying there in the late 80's as well and it may well have been Sunset by then. I think it was phased out shortly after that. Probably a good decision from the standpoint of keeping the lake clean, but I do miss that campground! It was a good "night before" campground.