Back in the early '60s before I attended school, I recall going to a local automotive garage with my father and him pointing out a huge engine on a stand out in the back. As I recall he told me it was a Merlin from a Spitfire - wish we had a picture from that day!

If you're ever into Hamilton Ontario and you time it right, you can enjoy that quad Merlin symphony:
Aircraft Details | Canadian Warplane Heritage Museum

This interesting article discusses and compares the two Merlins and their history (with references):
Rolls-Royce Vs. Packard: Who Built a Better Merlin?