I did a search before I asked, and didn't really find what I was looking for. The couple of posts relating to this spoke of wanting to do this, but I don't believe anyone posted that they actually went through with it. The posts pretty much just said that the big tanks hang low, and are ugly.
That's weird, maybe your search was limited to the "How To" section which is generally articles posted on how to do something. There's also a Gen 1 section with most of folks stories and build info, there's a lot of options which as why there's probably not a straightforward How To dual to single tank setup.
Here's some hits, you might also change your search words like single tank or Bronco tank, etc
https://www.nloc.net/vbforum/showthread.php/231617-Custom-rear-gas-tank?highlight=fuel+tank
https://www.nloc.net/vbforum/showthread.php/230071-Front-tank-removal?highlight=fuel+tank
https://www.nloc.net/vbforum/showthread.php/228730-Build-me-a-fuel-system-E85?highlight=fuel+tank
This is the Tank you want,..........
https://www.ebay.com/itm/38-Gallon-...245862?hash=item56d68545e6:g:lJUAAOSw0zdeVge5