Horn Lake, some 15 gravel km off the main highway has a nice rec site (pay) campground. It's a flat area, but I didn't pay close attention to site sizes. In general this is pickup camper territory, not 40ft class A with train.
I vaguely recall low(er) gas prices at one of the Reserve gas bars - because they didn't charge the provincial taxes. But my memories are decade old.
Google maps has streetview images as far as Tatla Lake.
For some history of this road, check The Road Runs West
http://www.amazon.com/The-Road-Runs-West-Chilcotin/dp/1550171410I suspect the biggest change from the 50s would be at the Fraser River Crossing. The original Sheep Creek Bridge (suspension) was replace with a big new one in 1962. Piers for the old one are still visible off to the side. The climb up Sheep Creek Hill is also much easier.
Also get the appropriate Backroads Mapbook (online or in groceries in BC).