They bolt right in. They sit up higher. I had them in Hack Job, but didn't notice they sat higher, because I also had the 99+ titlt steering column in there.
I remember you putting the newer interior in Hack Job however I've installed the rear seats out of a Mach and they are quite a bit narrower in my 92 coupe. How did you overcome this problem?
I used the bottom of the back seat from the 99-04 Mustang.
I had the stock notchback backrest recovered in 2001 GT vinal and pattern to match. Leather was a rip off and NO Mustang came with leather back seats from 99-04 anywyas. The last year for leather rear seats was 1998.