[SSS]

To get back on the subject, since you've defined your plan ($40 to $50k, BB, IRS, build yourself), you have already decided the major variables.

The most important item in your plan, IMO, is to build yourself. If you really desire to build the whole thing yourself from the ground up, then FFR is by far the best choice for you. They send you a frame, body, panels, and most of the accessories you need. With $50k you should be able to build a great FFR. It would be up to you at that point as to how well it would turn out.

Another very important consideration is how you will use the car. In my opinion, there are two reasons to have a BB in a Cobra. One, originality. Most Cobras replicate the 427 body style. Two, the bigger the better. As for point one, FFR is not the best choice to build an original looking car, simply because of the body shape. It can be done, though. Bob Rego's car is very original looking. As for point two, this is a matter of personal choice. In my opinion, a BB makes the car a bear to deal with as a street or track car, but lots of folks use them for both purposes.

As far as kit quality goes, you can get a lot of car for $50k. You can build a fine quality FFR with that budget. It would be up to you to do it right. There are other choices too, such as the new CAV SAI, Unique, SPF, Pegasus, Backdraft, and more. If you'd value originality over build-it-yourself, you should learn more about the alternatives. As others have said, you could buy a real nice used one and be on the road tomorrow.