This subject has come up quite a few times in the past especially how to deal with rusted gas tanks. I have always professed Phosphoric acid treatments. Here is a link to a PDF file on these products.
www.bapspaint.com/docs/psheets/PPG/Automotive/Deltron/P-226.pdf
I use these products regularly on almost all of my parts before refinishing.
74 Z1-A stock
76 KZ-900 Totaly stock vice MAC pipe
77 KZ-1000A stock
78 Z1-R 100%MINT 500 original Mi.
78 Z1-R Yoshi 1103 kit stage 1 cams Yoshi pipe. Etc
79 KZ-1300 (1400)
80 KZ-1300
81 Scratch built GPz1150R
82 KZ1000
