Basically, the cost of the swap depends on what you can get a motor for and how much of the work you are doing yourself and what you are doing for a tranny. It will also make a difference in what you actually get with the motor, if you get the motor only, it will cost a lot more than you are planning because you are going to need some wiring, if you get the harness and the motor, you still have to do a lot of wire splicing but atleast you have everything there to start with so you don't have to buy things that would be in the harness as you go a long. If you stick with the 4R70W I think you problaby need a Mark VIII PCM. If you are going with a manual tranny you will have to buy the manually tranny but the Cobra PCM will work just fine. I am going to say you can't do it for under $1500. And to do it that low would be finding a motor cheap and doing all the work yourself. I would say you should by no means expect to be able to do it that cheaply though. That does include exhaust too in the rock bottom swap price. And once again, if you can do it for that I will be surprised. If you check back for I dunno, the last 10 days, or just search in this section for my posts, you will see where these figures come from.
Former owner of 94 Bird with DOHC 4.6L swapped from a mark VIII
2011 CTS-V Wagon
1968 Torino was an original 289, C4, fully documented numbers matching car. Now: DOHC 4.6L/T-56 swapped, Cobra intake, IMRC delete, BBK long tubes and H pipe. Dynotech Aluminum Driveshaft, 9" rear with TrueTrac and 4.11's.