Obviously, this is my opinion and understanding, some of which may not be correct, but I think most of it is.
Before SAI got involved into producing CSX4000 cars, as we know, there were many different manufacturers out there, all with different designs. One of them was Hi-Tech, in Arizona, not the one in South Africa. It was owned by Tom D'Antonio. Unlike other replica manufacturers, they strived to reproduce the car in every way. They utilized the original chassis, but designed a fiberglass body and appropriate frame substructure to make the car less expensive, than by reproducing the aluminum body as well which was an additional $30-40K. Their price was $35K for an unfinished semi-roller, with aluminum doors, hood, trunk, with a fiberglass body, but not including wheels, tires,
oil cooler. Not a bad price. The diff was a nodular 9 inch modified to bolt into the original space, but still utilizing original style half shafts, etc.
There was a guy from my neck of the woods, I think his name was Tim Gunning, who made a lot of money owning the local Auto Trader Magazine. He somehow bought into Hi-Tech, and was a partner. Somehow, there was a falling out, and Tom D'Antonio sold out to Tim Gunning. There were other issues at that time with poor quality control, not delivering products as promised, etc., but that is another story. Hi-Tech has since gone under.
About the same time, SAI was not pleased with the replica market, for various reasons. They decided to come out with their own car. I'm not sure iif was arranged before D'Antonio left Hi-Tech or not, but soon after leaving, D'Antonio started working for SAI, taking the Hi-Tech design with him. Thus, birth of the CSX4000. The car was offered in both fiberglass and aluminum bodies. Price for an unfinished fiberglass roller was $42K, including wheels and tires. Aluminum bodies were available, hande made, at an additional $40K.
I believe most of the initial CSX4000 cars were fiberglass cars. SAI made the frame, body, as well as other components, and I'm sure farmed out parts as well. Then Kirkham came along, reproducing an aluminum car, much more efficiently and cheaper than what SAI was capable of obtaining them, so SAI ordered 100 bodies and frames from Kirkham, and then SAI finished the suspension, body trim, and interior components themselves. Thus, the birth of the Shelby-Kirkham.
In my opinion, all CSX4000 cars are genuine Shelby's, no matter who made the frame, body, etc. In the future, will some CSX4000 cars be worth more than others because of it? I don't know, and if so, probably by not alot.
If Ford stated making the 1965 Hi-Po Mustang fastback again, every part identical to the original, would it still be a Ford Mustang, even though they now get their toploader from David Kee? If they build the body in a different facility than they did in 1965, is it still a Ford Mustang? Yes, in my opinion it is still a Ford Mustang, an original Ford mustang made to 1965 specs, but in 2003. Would you buy one? He!! yes, but the Fed won't let them because it would not meet current EPA and safety guidlines. Well, SAI is reproducing the cobra, identical to the way it was in 1962-66. It is the second chance to buy one from Shelby. An original 427 SC I think sells for about $500-600K, if you can find one of the 30 or so for sale.
I don't follow the CSX2000 and 3000 prices much, but it seems that over the last several years, since the introduction of the CSX4000 and CSX7000 cars, the prices of street 289's have gone up, while 427's have been stable or maybe dropped a little. Do you think the introduction of the CSX7000 and Kirkham FIA cars have driven the price of the CSX2000 cars up, being that 3-4 years ago, the price of a new CSX7000 or Kirkham car was close to the price of a CSX2000 street car?