The 78 model had a small tail fairing as part of the back of the seat. I really can't remember if the mounting brackets are in the same location but I doubt it. The shape of the cover will be different too. If I were doing this job I would probably remove the seat cover and look for an aftermarket replacement or have one made (assuming the pan was still usable). Automotive upholstery shops are good at this. If the seat pan is rusted away then you are looking for a replacement seat.