I have the opportunity to trade my '12 GT500 for a '13 school bus yellow Boss 302. My 500 is black/red stripes, SVTPP, glass back roof and leather Recaros and 6200 miles. The Boss has the Recaros, Torsen diff and 8500 miles. It also has JLT carbon CAI, Roush axle-back and has been lowered with Ford Racing springs. I know that my Shelby (which is bone stock) is worth ~$8k more. What deal should I look to get if I decide to trade. What would be "fair"? This is at the local Ford dealer where I bought my 500 and many other Fords.