One issue that reared its ugly head when I was shopping for my Cobra was documentation! I looked at a car in Youngstown (Ohio for you out-of-towners) that had passed through at least two owners after it was built and had lost any information on who the builder was, exactly what parts were used, even what fluids were occupying the various systems. The guy who had it barely knew it was a "Classic" kit. It was the proverbial "pig in a poke".
Fast forward to the car I did buy. I bought from the original owner. I got the kit manufacturer's build manual, a binder full of installation instructions and information sheets that had come with various parts, drawings of parts the builder had personally designed and fabricated, and a book of receipts that covered about 95% of the parts on the car. I have a list of the fluids in the car when I got it, as well as recommended alternatives. I also have names and phone numbers of real people at the companies that built the engine, modified the carburetor, etc.
Knock on wood, I've only had minor issues with the car in the four years I've owned it, but it's comforting to know that the information is right there if I need it.
On a vaguely related note, if your location in Western PA is reasonably close, you might consider dropping by the Monday night Riverfront Cruise in Cuyahoga Falls. (That's also Ohio, in fact it's probably the only one...)
I'm generally there along with two or three other Cobras on a good night. If you check their website, (for Import/Two Seat Sports Car Night), my car is orange and white...and black......and silver. You can't miss it!