I took it to Techno strip, a chemical dip company in Etobicoke south of me,http://technostrip.com/restoration.html they have these chemical vats 20ftx8ftx6ft. Mostly they do industrial stuff but they also do brisk business in auto restoration. They can put the whole vehicle in at one time, grease, rubber,seam sealer, paint and rust are gone. All you get back is clean metal with a water soluble rust inhibitor sprayed on. So far I've used them for the frame of a Triumph TR6 and this gas tank, both came back perfect.
Once I get the Z torn down it's going to them for the big dip, I'll be taking lots of photos.