That's because they are all over here on the East coast! I've seen soo many for sale lately.
One thing you have to consider and I'm currently going through it is that if you put a built motor and big old blower on you'll need to swap out your fuel tank to an 03-04 Cobra, run twin pumps, and upgrade the transmission.
I went from a stock bottom end with lots of bolt ons plus a D1SC running 8lbs of boost, to ordering the 16lb pulley. Since I was already maxing out the stock block and fuel pump, I ordered the MMR 5.0 stroker, and all the fuel mods, plus a T-56, new clutch, etc...So while some may think you can just put a built 4.6 with forged pieces together, and stick on a big blower, you can't. Not at the power it's capable of.
Well, you can if you must, but you'll have a ticking time bomb. One day you'll pull away from a light rather agressively, hit 2nd, then third, and WHAMO! No more third. Or you'll hit it too hard on a warm day and you'll run lean because your injectors are maxed out.
Just my opinion, but I went through it.