What is the stock rear differential gear ratio on a 1993 Chevy blazer?

The stock rear differential gear ratio for a 1993 Chevy Blazer varied depending on the engine, transmission, and whether it was a 2WD or 4WD model. There's no single answer. You'll need to check the sticker on the driver's side doorjamb (or the glovebox) for the RPO codes. This code will help identify the axle ratio. Alternatively, you can physically look at the differential tag itself (usually located on the differential cover). This will give you the exact ratio.