Bacci: No. the spitfire used a rod for cocking, while the NW is a clone of the carter comp style. Sears on the hammer are different also. Your best bet is either to:
A: get a set of carter comp internals. check the diameter, but other than the NW anti-chop slant in the bolt, it should be a direct drop in. I don't know if Earons new internals are a match or not.
B: find a set of old NW comp internals. Is NW still around at all?
otherwise, you're looking at really custom stuff...