69 Z28 Hemi- Head Package?

[NCGuy68]

Its' my understanding that 5 sets of these experimental aluminum head packages were built by GM in late 68. GM saw no need for them in the Trans-Am racing series, and dropped them. Smokey Yunick dabbled with them for a while and Wayne Guinn has wrote about them in his book, "Camaro-Untold Secrets"

I know Al Maynard has a set on his 69 Z28 Cross-Ram car. I'am wondering what became of the other proto-types?

Thanks for knowledgable replys.