Honestly, I don't think that's a 987. If you look closely, the side mirrors are 986 style mirrors. The 987 mirrors have a vent in them as shown in the pic I attached below:
Also, the rear pic you posted shows a convertible top that looks like an aftermarket GAHH (which does not have a rubber seal surrounding the window). The OEM tops have a rubber seal around the window, as well as the extra rib in the frame:
So, IMO, that is a 986 made to look like a 987 Avalance. Lol