--> BC Adj coilovers w/ Swift springs 8k/10k
Bad idea. You're going to want to swap those springs f/r. Stiffer springs should be on the front unless you want to use it to mow the grass (the hard way).
--> Aluminum Source 1 ( black powder coated) Rear diffuser
I hope this isn't going to be some BS Poser diffuser - there are enough of those. Make it go from the cross-member under the axle back to the bumper at a 10-15 deg angle and it will generate some downforce.