The OEM SRT6 wheels do not need spacers; start by getting rid of the spacers and have the OEM wheels balanced.
A little farther down in this section you can find a picture and description of the OEM lug bolts.

I have the FK 510 on the rear of my SRT6. They require a lot more air pressure than the Michelin tires I usually run. The rear of the car was very squirrelly until I put 40 lbs of pressure in them. The are Okay, but I will go back to Michelins.