Dirt Tracker / Flat Tracker style seat?

Has anyone tried to fit a dirt/flat tracker style seat pan and seat on their XSR's or any other bike for that matter? Trying to see how realistic it would be. Curious if the fitting would be tough, what people have done in the past.

I'd like to fit something like the XR750 tracker seat on my XSR (I tried to post a link but was unable to since I'm a noob.


The last picture is the look I'm going for. I asked the builder of that bike and he said the tank and rear is all a single custom one-off piece.

Thanks in advance!