With as much money as you will have to put into the GT, just sell it cheap. Oh and yeah $6000 seems extremely high. When we finally located a car for my son, it was a 2 door 99 GTP with 90K miles, one owner, garaged, had the original order and sticker, old guy, that literally had a diary of dates and services performed, in beautiful condition. Purchased it for less than $6500. I thought the price was too high, but because of the one owner and how meticulous that owner was, my son got the car.
Why worry about the GP when you have the SS? Are you trying to limit the wear and miles on the Impala?