Cheapest route to super charge a 02 3.8L mustang?
first of all
supercharging a v6 is a very risky move because the engine is not built to withstand as much power as HO V8's are because of they way they are built.
my suggestion is sell the car and get a 5.0
it would actually be cheaper than making your engine compatable for a supercharger.
but if you want to supercharge, i suggest complete a complete engine overhaul with forged parts.