I didn't like it either. Just always puzzled the question. Too cold out in the garage to work so I am wicked bored. Time to turn on the Propane heater.
If you mean the backs were seperate and the base was a bench then that was a normal bench seat. dont remember for 68, but in 67 there were only 8000 of em. I LOVE mine. I had buckets in it for a while and hated the way they dump you to the center of the car during cornering, the bench raised center and armrest keep you right where you should be.
I have a bench in my '68 fastback and although I would rather have buckets, I've come to like the bench. Why not? The armrest is comfy and you'd never know they weren't buckets when your sitting in them. My '65 fastback had buckets and my butt doesn't seem to care one way or the other, plus it's something to separate your Mustang from the three gazillion just like it.
My little butt does not fit into any of the Mustang seats, so I am opting for a pair out of an Acura Integra. I plant to have them recovered to match the new interior, with the benefit of a headrest. Best of all $40 for the pair. Dark Grey with a Light Grey insert, for front and rear seats planned.