Jimmerz, bieng that you still owe money on the car, a 15k engine swap is not fiscally responsible of you. GOing the Bog Block route will also get VERY expensive, your suspension will have to be redone to accomodate the extra weight in the front and there will also be alot of fab and one off pieces involved to make it work. Also, to make that type of power, you will most likely have to have high compression and the engine will not run well on pump gas, to sum it up, your gonna spend the same money on retrofitting an engine thats not supposed to be in there, then you may as well just get porked and have a new Stang with no problems.
There are tons of more affordable ways to get a bad ass motor in there, 2V technology has come down in price significatnly, explore your options.