I fitted a genuine GT2 rear wing to my beloved. I removed the rear panel, that houses the tail lights / license plate. Drilled the holes for the wing bolts to pass through (either side of the stripes, in the panel after the hatch glass). I then made some strong metal brackets up, that bolt up to the wing bolts, and the stronger inner skin that goes onto the frame. (I understand that the GT2's have such a bracket.) I found it quite an easy DIY job, and must of done OK as wing has been fine at + 160 mph.
(I was so excited when fitting the wing, that I impatiently cut up my garden gate to source the metal to make the brackets...oops!)
Check with Dodge dealer / Partsrack, wing is about $1500 I think, and you'll need to part with about another $250 to have professionally sprayed your Viper colours. Warning...after fitting a wing you'll keep looking at it, not good to take eyes off road ahead when driving, take care!