In the not-too-distant future, 2067, human cloning is a part of everyday life. But it is a bizarre form of cloning; not actually the direct copying of a humans, but rather the construction of custom-made reproductions of humans using animal DNA. The CIA uses these so-called "chimeras" for various undercover operations, and one of their technicians, Simon Boyle, has a sideline making illegal copies: chimeras based on famous criminals, for rent. His Billy the Kid, a creation unable to comprehend or sometimes even recognize the sorts of things that didn't exist before the 1880s, is quite popular for a night of historically convincing passion with rich women, particularly the part where Boyle (as sheriff Pat Garrett) guns him down. As the story progresses, Billy the Kid starts remembering things from his previous lives. One of Boyle's clients sets Billy loose into the mean streets of the 21st century, where he struggles to seize control of the myths in his ROM.
Used availability for Rebecca Ore's The Illegal Rebirth of Billy the Kid
April 1991 : USA Mass Market Paperback
October 2012 : USA, Canada, UK Kindle edition