As a good overall package (good on street and strip), I'd say Q1A shocks (adjustable), instant center brackets, air bags and slicks. I had all of the above except for instant center brackets and could barely manage low 1.9's. After the brackets, I'm down to high 1.7's with decent track prep. I set the shocks for 0 up front and about 8 clicks on the rear. I have airbags set at 20psi on the right rear and about 5 psi on the left. I have ET Streets at 18psi with a medium burnout. I also have no swaybars front or rear. You can disconnect the front at the track if you wanna keep it for the street.
Metco has those brackets but i'm not sure if they have them for the Caddy but it doesn't hurt to ask. If the arms are the same for the b-body, then you are set.