I know this is a long dead thread, but the concept K5 is still for sale. I attempted to purchase it. The reason it's stayed for sale is because it is impossible to finance without pulling from your home equity or retirement fund. So you would have to pay cash, current asking price is $22,000 and it is sold Bill of Sale Only... There is no title and it has quote "an incomplete VIN". It MAY be able to be titled and registered but that depends on your state... I never heard an answer back from mine because they kept giving me their opinion instead of the law. As for the soft top, I think they simply threw the top from te S-10 "Shark" concept on it. It's about the same size and the one on the K5 looks far too small.
In conclusion I could have bought it but for $20-25,000 you can build much cooler stuff and even buy something like a 69 Chevelle or otherwise.