Right then. Just did a bit of research on the nose cone dimensions.

As it turns out a shorter nose cone on a P51 means its probably off a different model because the earlier versions had a shorter nose cone due to the fact of the carburettor being located above the engine. However the longer cone is from the P51d because the carburettor was then mounted below (small scoop at the base of the prop)

Hopefully that clears it up..... But I'll see once I get the propeller on to finalise that.

check out the images...

Jay