I think 4" is a bit too much... you'll change the whole suspension geometry with a lot of camber causing uneven tire wear and performance loss, and you'll rub your fenders to boot.

Try a 1.5" drop up front by cranking down the torsion bars, and a 2.5" drop in back with some custom coils. You can get some made for you for abou $200.

I tried to do this with a set of springs from Valley Custom Springworks, but the coils they made for me didn't achieve any drop. Do a search on valley to find my drop threads. I suggest that if you want to pursue this, go with a local spring maker and have them test the fit of the springs before paying them.