There isn't any kind of single maintenance or parts manual for Crowns. They were always ordered and specified with different components as requested by the buyer. The only kind of maintenance information books I've seen were essentially three ring binders which included information from the various manufacturers of the components installed for the customer. Depending on the specific equipment being installed there would be manufacturer manuals included for each piece of equipment. Engines (DD,Cummins), Transmissions (Fuller,Spicer etc.), rear-ends (Rockwell, etc.) Air compressors and air system components, (usually Bendix), any number of other pieces of specific things included in that particular build.
One of the great strengths of the Crowns is that they were a Coach and Body building company, who bought and installed various kinds of drive-line and body accessories for the customers individual needs. This is one of the reasons why you can still find and buy most all of the important parts and components today because they are essentially still off-the-shelf standard heavy duty truck equipment parts. Even if not currently manufactured there are still untold quantities available and even replacements designed to fit right in. I would suggest acquiring parts and maintenance manuals for your Crowns' specific installed equipment from the original manufacturers of that equipment. You can then re-create essentially what Crown gave to all their customers back in the day. You can even go farther by getting all the information you can find on all the little stuff like switches and relays, lenses, lights, etc. as much as you want. This will help you when the time comes to track down a replacement part or how to find a newer one that supersedes an original part number. Remember you can use anything you want and customize to your hearts content, because that's what Crown did when they were new. As long as it functions as it should or even better than new, it's your bus now so have fun. There is no right or wrong way to do things, only what works and satisfies you. It's a customization free for all for those that enjoy that kind of stuff.
Crowns were not like any other bus manufacturer (except Gillig), because they didn't design and incorporate a lot (not none), proprietary parts into them with the idea that people had to get them from them. You see that today all the time when folks need a part for some kind of XYZ brand, of a particular year and model, just to find a headlight assembly or something else proprietary in design for instance..... Crowns were essentially kit-built with commonly available parts and sub-assemblies.
This may not be the answer you were looking for, but it reflects the true facts on how Crowns were built and supported once in the field. Learn all you can about what you have on-board and compile a binder with the information you need to find and get replacements, and carry it with you so that you'll have it an hand on the road if you ever need it. Enjoy it.