thanks for the info, I figured it was in that neighboorhood too.
Stock frame but I don't like covers on anything really, I like the mechanicals to show and that whole area under those covers is butt ugly. So some judicious measuring and figuring and I think I can get a tank fabbed to fit along with hiding the battery. Of course since I moved the fuel pump under there I have to do the pumpless fix too to get it out of the way. if it isn't one thing its another.
It may be a pipe dream but you just never know until you start tearing stuff apart.