Welcome to the forum. I have an 89 Winn Chieftain. It had the owner's manual, however, I was able to get the wiring and water diagrams from Winnebago. I just sent them an email and they forwarded files for the wiring and water. They have been super each time I have had to send a request or ask a question. I'd check their WEB site, send customer service an email and go from there. Good Luck
Sorry, if you can't get one....then just ask away on this forum any questions you may have. There are a whole lot of fantastic helpful folks on this forum. I've learned a lot and saved a bundle by applying suggestions/guidance that have given to me.
If you haven't contacted Winnebago you may want to. They keep records for everthing they ever built. You will need to find the data plate usually below the drivers window. Take down all the numbers and their designators (ie mdl#, ser# ect.). With this info they can find almost anything for you.