Nice save there!
We have a '73 Dodge Yellowstone Premier class C. I have searched all over and never found another, not even a picture or brochure. You can imagine what a google search of "Yellowstone RV" or the like brings up.... I know that it is the same Yellowstone as the classic travel trailers and have seen quite a few of those even locally, just never a class C.
That being said, most of the house portion absolutely used the same basic materials and designs as most of the others of the era, including some of the Winnebago's (bathroom wallpaper for sure). I completely redid most of the house electrical, both AC and DC, to my own design specifications and redid the entire water system, so those vintage items are no longer an issue to deal with.
The chassis is very straightforward otherwise. Parts availability is great for most items other than a few exceptions (newer 16" wheels, brake drums perhaps...). I would highly suggest, from my own experience, that you spend the time and money on getting the suspension restored and updated after getting the basics of the RV water tight and solid again. I redid the front suspension ball joints and bushings, added Hellwig front and rear sway bars, replaced the steering box, idler arms, shocks, 16" rims and radial tires, and added air bags on the back springs. This took mine from a vehicle that was a serious white knuckle driving experience that was no fun at all (actually frightening) to drive, to a vehicle that could be driven comfortably at highway speeds without issue. I also added a front spoiler and fabricated a deeper front rubber skirt under that to control air flow underneath. This helped stability quite a bit and even fuel economy a little. These changes truly transformed the way she drives.
It has been a lot of work, and will continue to be as it still has things to do and always will, but we love it. Always gets looks when we use it as people don't see many of these around anymore. Lots of thumbs up and some great stories from other campers reminiscing about the ones they used to have years ago.
Your perseverance will be rewarded with a very cool RV once you are done!