I contend that the 3-liter Taurus version of this engine should have been the standard Cougar motor from the start. The engine is exactly the same size (same block) so it should fit fine, and the extra 30 hp would be nice.
The biggest thing one can do to a V6 near as I can tell is a supercharger. I think the Paxton unit advertises somewhere in the neighborhood of 250HP, which would be about all you'd want in a Cougar without some other accomodations such as bigger brakes, etc.
I believe the 3.0 Jag version of this engine is around 230hp, so the blower would be a bit more power than that and probably a whole lot cheaper.