So after a bit of reading, I stumbled across a fairly complete post about differences in North American gauge clusters. It looks like my assumption was correct, the gauge cluster was intended to match the crank in the 89 models.
Thanks to Jeff Lange from supraforums (he wrote the post that I'm copying here lol)
Canadian:
- Speedo in km/h
- Oil Pressure in kg/mm^2
- Turbo Pressure in mmHg
US:
- Speedo in MPH
- Oil Pressure and Turbo Pressure in PSI
- Fuel gauge says "UNLEADED FUEL ONLY"
- Has light for Security System
Automatic Transmission Models:
- Have 2 extra lights on the tach for Transmission operation
1986.5:
- All gauges have small marks between the major marks (a lot of them)
- 6500rpm redline
- Speedometer goes to 150mph (240km/h)
- Check Engine Light, Open Door Light, and Taillight Failure Light are all white-outlined
- Needles are all orange, including across the centre section
- Super Monitor optional
- TEMS optional
1987:
- Turbo Pressure Gauge added on Turbo models, replacing the N/A's voltmeter
- Turbo models have different circuitry on the tach (due to a different type of ignition system)
1988:
- Word "CHECK" added under the Check Engine Light symbol
1989:
- Some have 6500rpm redline, some have 6250rpm redline (depending on which crank it has)
- Speedometer changed to 160mph (260km/h)
- Small lines removed from gauges
- Needles changed (orange part on centre section removed, center section bezeled, instead of having a protruding block sticking out of it)
- Needles on tach and speedo made longer, as numbers are moved further out
- Super Monitor no longer optional
- "CRUISE" light added on tach (corresponding to change in steering wheel type)
- Check Engine Light, Open Door Light, and Taillight Failure Light become black outlined, only visible when they light up
- Colour of clock changed to match more closely with the rest of the illumination
1990:
- 6250rpm redline
- Airbag light added on Speedometer (between seatbelt and brake lights) (US Only)
1991:
- Extra lines added on Speedometer to make it fit more with the other gauges (US Only)
Carry-Over from 1990 (Canada Only)
1992:
- Airbag light added on Speedometer (between seatbelt and brake lights) (Canada Only)
Carry-Over from 1991 (US Only)
Original thread
here