Either you select different model of transportation that has larger space to accommodate taller people or ditch the rear seat, move the front seats back to what ever distance you two will need and you shouldn't have any problem with the fact that seats being powered or not. (all mechanical moving parts of power seats are above the seat mount that gets bolted to the floor board) You might want to rebuild the left over rear section (if any) and extend the trunk area. (to accommodate bigger speakers/amps maybe or increase storage space)
Personally, I find rear seats in Trans Am, Corvettes, Porsche and whole slew of others a big waste of $$ + space. I don't think anyone in the companies building them ever actually tried to ride in the rear seats because if they did it's very unflattering of any automobile that accompanies such vehicles with relation to their price tags. Anyone over 4" tall couldn't possibly fit back there comfortably. (I could be off by few inches or so) If buying an auto was judged by the rear seat ride comfort they be out of business.