Karmann Ghia convertible rear seats are smaller in size than those used in the coupe, so if those came out of a KG coupe they will not fit in the back of a 'vert.
Coupe rear seats are about 40 3/4" wide, while 'vert seats are only about 35 1/2" wide. HTH
Vince http://www.karmann-ghias.com/
I decided to recover the rear seats on my '70 Vert. As I took things apart, I found crumbling foam, rotten wood, etc. Ended up actually remaking the seats with some 1/2 plywood, new foam and the TWI seatcovers. It was truly no big deal, and looks far better than the originals.