Yes, +heyduke john
the Medicine Campground (third one in on the loop) has plenty of space for large rigs. Our favorite Al Hogue has a few big rig sites, the first campground on the loop, Hemlock, is not as big rig friendly, with very unlevel sites. It is better for tents although we do see motorhomes and trailers in there. The road up through California from Highway 299 is narrow but perfectly fine for big rigs. The road west from Highway 39 and Tulelake is narrow and a constant grade, but a big rig could do it. For some reason that road, although paved, is incredibly rough.