What type of tires to you run/race on? Square sized or staggered?
2.75 isn't outside the ballpark for a car on R-tires or slicks. For a track car with aero (which adds normal force at speed) it maybe puts it in the ballpark for a good street tire.
What stands out to me is the disparity between front and rear. Your ride frequency split is a good starting point for a FWD race car on street tires :-)
If your front ride frequency was raised to 2.8-3.0 and you had a square wheel/tire setup with sensible bars and alignment, I bet you'd find the car was fairly well balanced - without having changed the rear. But overall those frequencies are a little high for surfaces that aren't pretty smooth.
Every car is different, and what's best depends on the type of racing, level of grip (at each end), and power levels (including where it gets sent), among others.
For a decently balanced and moderately powerful RWD autocross car on good modern street tires, I like starting around 2.5 front and 2.2 rear. The higher the power for the grip level, the bigger the difference I'd probably end up with - a Miata might be 2.5/2.5, but a Corvette I might go 2.7/2.1 - the reasoning being, the more powerful car needs to work the drive tires a little bit less in the corners to make use of its power. Obviously swaybars and their contributions come into play and can influence the resulting frequency splits.
Smoother surfaces and higher grip tires trend those numbers up; rougher surfaces and lower grip tires trend them down.
Good luck, have fun, be safe on the streets!
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