My Rand McNally shows the Going to the Sun Highway in solid red. And the McKenzie Pass state road is in the narrow red of "other through highways". As an Oregon native, I've traveled it many times, but not in an RV. It's not that it can't be done. It's just that it's enjoyment would be diminished by the necessary deliberateness in its negotiation and the angering of other travelers I'd hold up in the process.
I was kinda hoping, Bill, that you'd mixed up the McKenzie (River) Highway 126 with the McKenzie Pass 242, or perhaps misinterpreted Dick's question, because I wouldn't describe 242 as a typical Oregon highway, but 126 certainly is.
Joel