[Stocker]

All I can recommend is the only one I'm familiar with -- Skyjacker Softride (2 1/2"). I put 'em on the front of my K20 several years ago because the OEM springs were sagging badly. Quality is excellent, ride is decent, and I still have no complaints. Only difficulty was the bushing inserts (they use poly bushings BTW) were a smidge too long for the front hangers, and I had to grind them off a bit so they'd fit. I never did install the rear blocks. They also make 4-spring kits if you plan on replacing the rear springs too.

On a related note, you'll need longer front shocks. Just so happens that stock rear shocks are the correct length for a 2" to 2.5" front lift. No other changes needed -- steering arm is OK and brake hoses are long enough.