[Jabunga]

I'm looking for a bit of guidance. I would like to source a tank and seatpan (or finished seat) for my '77 xs650 cafe project. The bike is currently wearing a very nice set of clip-ons that I aim to keep in place. I need to know what to really look for in searching for a tank. What measurements do I take? Does anyone have any ideas about tanks that may fit and look good. I'd like light (of course.) I've been told that early 70's Ducati 250 tanks will fit with minimum of fuss. What's the viability of fiberglass, how difficult is it to fit a fiberglass tank and seatpan from a manufacturer (such as Airtech?) This is my first bike project (hence the use of XS650.) So if I sound a little clueless, forgive me. Does anyone have a line on aluminum tank$?