I have a few early ('60-'62) GMC Suburbans and they have the tracks. All of my Chevy Suburbans, have the oval plates mortised into the floor, with the elevator bolts, for mounting. The later GMC Suburbans, I have, also have this configuration. I will see if I can come up with some photos of the bottoms of both style seats, as you mentioned, in order to determine the differences.