[JayBar]

Excaliber , FYI while the Backdraft uses BMW suspention parts ,forward of the differential is the builders choice for engine and trans. Yes a FE will fit, if a 4.6DOC will fit so will the FE.

As to which kit to pruchase the most important thing is not to be duped by the manufacturers projections. No matter how long it takes and how good a wrencher you are parts cost what they cost. I built a Basic FFR (302ci) and had $23,000 in it.
Your not going to buy a kit for 12,900(plus crate and shipping) and a wrecked Mustang for $500.00 and spend 4 years and end up with a Cobra.
Check out the information on this forum. It will give you a "feel" for the real cost of a decent Cobra.