I believe the chassis is the same. The 1991+ dash should fit your early car. To connect the instruments, you'd need the wiring diagrams from both cars.

The big problem would be the speedometer. Your early car has a 12 pulse tone ring, and the late car has a ABS tone ring with about 96 (or 108) pulses. In my experience, the two sytems are not compatible even if the pulse count was the same. If you had an ABS car, the instrument cluster conversion should work, but not on your early non-ABS car.

If you could transplant your early speedometer in the late cluster, you'd be good to go.

We installed an ABS rear end from a 1991 940T in my son's 1984 760T for a couple of months. I even got the factory signal convertor from a late 1987 740T, and I never could get the speedometer to work. We went back to the 3.54 ratio stock rear end in order to have a working speedometer.
--
john