ask and you shall receive.
I have a bunch of tanks im trying to unload if you are interested in something that is similar to that idea.
here is the link to the sale page, also check out the install link within that link, showing how I put it in a 123 chassis-
http://www.peachparts.com/shopforum/mercedes-used-parts-sale-wanted/341976-aux-fuel-tanks-buncha-18-couple-12-gal-%24100-dollars.html