I didnt do one in a 4th gen f-body, but first thing that comes to mind is mounts to the frame...
They might have had to weld the GN frame pads to the frame of the car, and had to make sure they put them in the right spot so everything would mount up right. Also dont know if the DP becomes a problem either... it might.
I would see if that person is on these boards somewhere, because if they already did it, you want some advice.
Just my 2 cents.