Nice one spiky, i bought a base model mk1 sierra for my track car, no sunroof, no leccy windows, no sunroof, no fuck all. Even the bumpers are lighter than normal,so a lot of weight has been saved already. Hope to see what it will be like up against your tin can in the wet sometime soon.
I run kumho ecsta's off a new shape mini cooper rally car, and they are awesome in the wet. Cheap as well (free).