A 1/2" sounds like a lot. Not sure the pin depth would allow for that much. I was thinking what I read was about 10mm but I can't remember now. I did a search but came up dry.
I remember a thread here on CC where David Kirkham rebuilt an original rear suspension. You might look through that and see if it shows anything about an original hub length.
Original 427 Street Cobra Suspension Rebuild
Larry