Hey Brad, I'm using a donor "Coyote" 5L engine from a 2013 F150 with a TKO600 tranny, it all comes down to how much work you want to give yourself. I paid $2600CDN for it and will be doing minimal upgrades this year. just tore it down and will be starting to prep it for paint and then will rebuild it from the bottom up. A few items that you will need to make sure of is the timing cover and oil pan needs to be changed out, they need to come from a 2013 Mustang GT engine. Other than that the wiring needs to come from Ford Performance (ECM). Browse the blog as there are many people doing the smae, again, how much work do you want to give yourself other than building the car. (my advantage is that my son is a mechanic so the fear of doing the engine mechanical work is minimal)