1992 Speedometer cluster

What is the difference between the Ultra and non-Ultra clusters? The only cosmetic difference is the "Premium" fuel label as far as I can see. Are there electronic differences as well? I have to replace my jumpy inaccurate speedo/tach and am having a tough time finding the Ultra version.

Also, can you post the correct part numbers for each?

Sorry, there's a similar post in the Lasabre area. I'm a sucker for 90s Buicks. I'm on my 5th vehicle!

Thanks,

KennyC