[VetteVet]

Just some thoughts based on what I know (and some of what I think I know). I'm not putting this out as gospel, just the way that I understand things to work.

As far as I know, the only dash info affected would be the fuel economy information and possibly the tach. The oil pressure, coolant temp, oil temp, fuel level, etc. should be OK since they have dedicated senders feeding the dash directly.

The tach could be a problem because the 89 gets it's tach signal from the ignition primary circuit via a tach filter. The ZR-1 tach signal is a 5 volt TTL level signal generated by the Ignition Control Module. If the 89 dash will trigger from the TTL signal, you should be OK.

The digital dash gets information for fuel economy, range, etc. calculations from the ALDL data that the ECM is broadcasting. There are different datastreams used, depending on year, model and ECM. This will lead to problems.

For example, if the dash is looking for byte 6 in the 89 datastream, the same byte in the 90 ZR-1 ECM datastream will more than likely not be the correct piece of information that the dash needs. Thus the info displayed by the dash will be erroneous.

With that being said, the code that the 90 ZR-1 is running can be modified to broadcast a compatible datastream. The downside to this is that the modified datastream will now cause problems with diagnostics when a scan tool is hooked up.

I don't think any of this is insurmountable, just pointing out some of the problems that you could possibly run into.

Jep