Hey Robert,
I bought the Model 711. It has the 3 tanks + battery levels - same as original equipment. For about same money you can have ambient temperature display when the levels are not showing. Model 711T. I opted not to have that.
The levels are displayed as % of full tank to a resolution of +/- 5%. The sensor strips are 16" and can be cut to required length dependent on tank height.
I have already extensively modified my instrument panel to accommodate instruments for monitoring my solar installation. I will be modifying the relocated control panel by cutting off the top portion used for existing tank level monitor and replacing it with the new display. The SeeLeveL display, at 4.75" x 3.25", is just slightly wider than the current panel and also taller than the section I will cut off. I believe I can make it look pretty good but it will require re-positioning in my new instrument cluster. You can see what I am talking about regarding my modifications by
viewing some pictures here.
My method is not required and the new display can be installed anywhere you can find space. A good place would be the wall to the right of the stairs in the same area as the closet. There is a false wall and space in there to flush mount the display and route the cables. The existing monitor would remain intact.
Hope this helps.