There are plenty of Merlin engines around.

I landed in Salinas CA and a guy came by and took me over to his
hangar. He was building NEW Mustangs. At that time the price tag was
about a million. I asked him about engines and he said there were
plenty, have to be rebuilt of course. Not sure why that is, perhaps
they kept the engines around when they scrapped the airframes. The
design is in the public domain. You never hear about this operation,
maybe he never continued, this was about 4 years ago. But he did
complete at least 2 or 3, I believe.