Well, if this is where it's going to be discussed...
CT is most likely requiring a DOT approved belt. Last time I looked none of the racing harness systems, 4 point, 5 point, Simpson, Crow, etc. that are DOT approved. But I just google searched and this showed up:
https://www.schrothracing.com/post/s...egal-harnesses
Although it seems to refer to harnesses that attach to standard 3-point systems rather than being DOT approved 4-point systems...
So you might be able to swap out for these and still keep the harness style in the car. I didn't look to see what kind of mounting system they use but the ones I used in the Cobra and GT used a kind of eye hook and double snap.
Now as far as racing harness expiration goes.... That matters if you're going to track the car. I was at one event and they mentioned to another participant that his harnesses were expired but they would let it go. I suspect they are a little more relaxed for amateur track days than pro
The reality is that for street use the age is irrelevant - else DOT approved seat belts would also expire and there are lap belts from the 60s still in use... My observation from my harnesses is they were much sturdier than what you find in most vehicles especially after a few years with frazzled webs...
For expired harnesses I recall one would re-web but the price wasn't that much different than a new set. Others won't re-web at all.
So I'll ask a question similar to the one I asked in an Australian topic: If someone wants to register an original CSX2000 or CSX3000 Cobra, will CT make you put in a 2023 seat belt??? To me "replica" means as it existed then, not as you'd like to have it exist now. If that is the goal then just get some Cobra plastic and mount it on a Miata body.