The -9 Merlin was the version used in the postwar P-51H. Air racers in the '60s and '70s, including hydroplane teams, preferred the -9 over the standard -7. I think today they build "hybrid" race Merlins using transport con rods and other mix-match parts to ensure longevity.
That spare Merlin looks to be on the original wooden shipping dolly that Packard mounted it to in the late '40s.
Also, the N54xxV series of FAA registration numbers was assigned to a few dozen P-51Ds in the very early 1960s. I believe an aircraft broker in Minnesota reserved that series of N-numbers for the Mustangs he bought surplus at McClellan AFB's famous auctions of 1957-58. Rows of flyable P-51Ds up for auction and not one of them more than 2,000 bucks. Those were the days.
N5416V:
http://www.mustangsmustangs.com/p-51...erial/44-84896