I recall from many years ago a photo in a book, possibly William Greens "Warplanes of the Third Reich" where in the '109 section, there was a black and white photo of a dark coloured '109 fitted with a Merlin. The spinner was lower than on the DB powered '109s and the cowling had a marked droop along its top surface. It looked ugly compared to the DB powered version.
I may be wrong as it was close to 40 years ago when I admired the book and the aircraft in my high school library. Perhaps if someone has the book, they could check for the photo that I recall?