There is another nuance that these pictures clearly show and that I was unaware of until Fran Hall put me straight: the difference between a Mk I and a MK III nostril panel. Apparently, many kits actually have Mk III nose panels. If you will take notice of the position of the nostrils in relation to the outside edge of the nostril panel on the green car, you will see that there is only ~1" between the nostril and the edge. Also notice the corresponding distance between the inside edges of the two nostrils. The nose panel shown on this car is a true Mk I nose panel. On the Mk III (see pic of my car here), the nostrils are set about 3" closer together and as a result have a much wider area between them and the outer edges of the panel.
The difference is not insurmountable if you are trying to interchange one for the other, but do be aware that there may be interference issues dependent on how the recessed lip on your nose clip was formed. (External dimensions seem to be identical, or nearly so.) In my case, putting a Mk I in a hole for a Mk III, I am going to have to relieve the inside vertical corners of the nostrils and/or the inside front corners of the panel opening in the front clip. Luckily there is not interference with the routing of radiator lines, etc. under the panel.
Regards,
Lynn