Deacon's tank is off either a B or C model 77-79, the tanks are the same between those models and years (other than paint that is). I think slapping one of those tanks on your bike would help achieve the horizontal line you're looking for on the front because they drop down more over the frame spine than the LTD style tank you're running now. They mount basically the same way, so it shouldn't be a huge pain in the ass to do the swap either.
thank anarki, i'll check that