The yellow one is located in Maitland Florida at Rogers Corvette Center
http://www.rogerscorvette.com/ The white one is in a private collection in Washington state, I used to have a link for it but I'm at work so I don't have it handy. There is also a guy who goes to the Carlisle-PA show who has what he claims to be a ZL-1 although as far as I know he has yet to provide any proof, this car is red.
There were more than 2 made, however only 2 cars were documented as being sold to the public. I've seen the yellow one in person on a couple occasions and talked to Roger quite a bit about the car, it's absolutely spotless. He purchased the car at a US Marshalls auction for roughly $300,000. The car had been in the possesion of a drug dealer and was not in great shape. I have pictures of the yellow, white and red cars but no way to post at the moment.