One thing I liked about these bikes back in the early 80's, is that parts were easily available. I bought this 1975 Z1-900 for a couple of hundred dollars with many missing parts. Took the cylinders to Orient Express in Long Island for a 1015cc bore job, installed a set of 29mm smoothbores and a used Kerker exhaust.
I don't know anything about auto body repairs but I tried to make the bike look similar to the original 1974 colors using spray cans and car pinstripes from auto parts. I began preparing the tank, sidecovers and tail during winter time. I didn't know any better, so the bike was painted in my basement. That spray can paint job lasted at least 5 years.
That bike took me on a cross country trip from Brooklyn to Phoenix, AZ and back. I was fortunate that the only minor issue during the entire trip was having a flat tire in Meridian, MS.