Common gear ratios for the 1997 Z28's 8.5-inch 10-bolt included:
* 3.23: This was a common ratio.
* 3.42: Another popular choice offering a bit more acceleration.
* 3.73: More aggressive for better acceleration, but at the expense of higher RPMs at highway speeds.
To know for certain what's in *your* specific 1997 Z28, you need to:
1. Check the axle tag: This small metal tag is usually located on the differential cover. It will clearly state the gear ratio.
2. Look at the build sheet: If you have the original window sticker or build sheet, it will list the rear axle ratio.
3. Check the RPO codes: These codes on the build sheet can help identify the rear axle option.
Without checking one of these sources, you only know it's likely an 8.5-inch 10-bolt with a gear ratio in the range mentioned above.