I just dropped a set of 98 buckets into my 68 this weekend. Wouldn't describe the install as 'a breeze', but turned out to be that I didn't have the right tool to pull the 5" high tracks off the 98s and swap with the 2" high ones from the 68. (Anybody interested in a pair of blue 68 seats, decent condition, currently located in NM?)
The trial by fire, though, was while I was installing the seats. The box with the hardware for replacement seat belts was in the car. So was my 2 year old. After awhile I noticed that she was being very, very quiet...she had thrown the hardware, one piece at a time, into the box around the shifter where a gasket should cover up the hole.
Took it apart down to the newly installed carpet and fished with a magnet and forceps...all pieces were recovered, but the air was blue.