You could do a rag top like they did on the old Nashcans or Citroen 2CV. Leave the sides in place, add a support between the B pillars. A rag top should be easy to fabricate from there.

It'll be like having a sun roof from the windshield to the rear deck.

http://www.secondchancegarage.com/public/197.cfm

http://www.2cvsrus.com/restoration/dolly_pavel/frame_e.htm

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