Ian, those are the same as was on 1967 Mustangs. They are wider, shorter and more "script" to me than the more block lettering on the original street GT cars. These are the letters I used on my car. Although not completely original, I think they are a cool addition and not many replicas have them on as most guys are after the race coupe trim.
I was just posting pics of the the FORD letters as found on various UK vehicles during
Here's a link to a close up of one of the GMP road car models - it definitely appears to
be more of a block lettering type than the Zephyr used:
GMP 1/12 Ford GT40 Mk1 Road Car: Blue With White Stripes, GMP, Sports Cars Exotics, Auction, Diecast, Collectibles, Apparel, Hats
But, it could also just be the eye playing tricks, and that the larger spacing between
letters makes the GT40 look more "blocky".
The Brian Winer/Wallace Wyss GT40 Photo Archive book has a good picture of the
letters, I'll see if I can dig it up.