That's the textbook ideal rear for your (as-stock) vehicle unless you need to go back and run 0 offset wheels. Or need a strength upgrade. An '88 Formula starts life with a choked-head-intake ports engine, or a choked-port-intake-mani that is matched better to 3.42 than it would be to 4.10. Drivability around town and country is better with a 3.42. Unless you're putting mega hwy miles on, or otherwise prioritizing mileage and need to keep the 2.73, go for it, absolutely. A V8 '98 was an Auburn, with an SLP Torsen option. Ideally, a '99-02 rear has a standard (no frictions) Torsen, unless the car was SLP-"upgraded" to an Auburn those years. Your tach, speedo, math or all 3 are off.