@Michics , what's your status? Ford 7.3L is strong, at least the later yrs, parts are common.
Overall, headroom is not *really a problem (I'm 6'2", GF is 6', my module is 5'7"), but ask me again in a year....
Selling feature: cut a footwell box into the floor (at the stove)-- even if its only in one area, provides relief to GF. Entry door step is another tall area; pad any corners. Just *how much standing do you do on the sofa?
I'm planning to convert my rear left box to an interior standing shower @7'1" for her. Day-to-day use will be interior food prep and exterior storage. Yes, that means removing the aluminum top of that box and sealing/insulating around the remains.
Hopefully, I'll be popping the top sometime in future [to produce headroom on cabinet side (port/left) and a second floor(!) for sleeping and bug-free lounging].
Remember, the *point is to live OUT OF the truck, not stay inside it.
True enuff, its tighter than an RV!