Hi Birdy, I had the same plan myself, although I haven't started any demo yet. I would recommend getting the service manual. It is available online as a pdf document, for a few bucks. I believe that you order the manual specific to your year. It will show (at least for my year (1973)), all
of the different floor plan specs for plumbing, wiring, heating, etc. I have also noticed that in the 73 Sovereign
, the windows may pose a problem, in terms of placement.
I am going to watch your forum, I am very interested in your progress. Don't be shy with the pics.