[surfbeast]

You would be left with a car you could not sell for anything and would be a major pain to do. You would need a lot more than the engine, lots more. The "A" plan basically saves you ten percent of window sticker, maybe more. The a hole dealers just give you that much less for your trade to make up the difference. If you have cash and can combine with other discounts it helps out alot.
Buy a 99 GT for about fifteen grand or less, they are everywhere or buy a good rebuild. mine was way less than ten grand.

Good luck