Well, so far I have talked with a couple of guys who are more well informed (smarter) than me, and one said he seemed to recall these tanks came with a red paint or primer inside to prevent rust from the factory to the owner. My auto mechanic who owns bikes, said he didn't think there was much rust, if it was rust.
I did the old drain gas into a coffee filter and see what comes out trick, and I find a little bit if real fine black or dark brown grit. I've seen more on local girl's teeth than in the filter. I still need to take the tank off, give it a good sloshing around part full, and see what the coffee filter shows.
Then I will pull the petcocks and clean the screens, and make a decision as to just doing a paper inline filter, or roll some BBs around and do an inline, or try something like Evaporust.
I prefer cheap, simple and effective. I don't think I will need to line the tank.
Also, I jump started it and rode it to warm the oil. It idles, runs and shifts like a top. Some seeps from gaskets (like an old tractor) from over the years of sitting, and the plugs are black like too rich. Not oiled up though, which is good. All the lights and switches work, and somebody installed a world class horn-- no Roadrunner beep, beep....
Mechanically, I need a tach-- the needle is gone. Wonder if you can rebuild those? New tires, and battery, plus, filters and fluid changes. I will take the MAC 2 into 1 pipe off and go back to stock 2 pipes.
Cosmetics-- the battery side covers and tool tray are gone. Wish the little chrome grab rail around the seat wasn't gone. Otherwise she should be pretty slick when she cleans up-- very little rust on the frame and chrome.
So, she won't be showroom when I am done, but I won't mind being seen on her because she will look pretty good for 35 years, and 27,000 miles.....at least after I ditch the German fairing that came with her.