You can sleep in a 90 (as long as you're not too tall) by running a hammock from the mounting for the rear view mirror to just above the rear door. Not to comfy mind.
There was a guy in one of the magazines a good fiew months ago had a dormobile kitchen in his 90.
Anyway, I'm converting Edith to a camper / expedition 90 at the moment and plan on having cooking facilities and cupboards, a sink and shelving down one side of the rear (with no window), and a bench on the opposite wheel arch with a window behind it and a fold down bed platform inside.
For extra legroom when sleeping, I've got a hinged upper and lower tailgate to replace the back door of the hardtop, and with the upper tailgate (from a series 2) up, and a cunning velcro or pop studded bit of canvas between the two tailgate parts, I get an extra foot and a half - so ample space.
As the job proceeds I'll post pictures. As it Is my new GALV chassis only arrived this morning, so a long way to go yet!