Trevor,
I hope you don't mind me scanning a picture from your book...
Here is the Brian Angliss AC MkIV body bucks. The one on the left does look significantly different than the pictures from Gary's gallery. I don't think the buck on the right looks like the one from Gary's pictures either.
However the AC MkIV body is different than the 427 Cobra body, so a new buck would have been made just for the AC MkIV body. The assumption is that the pictures in Gary's gallery are of a Brian Angliss replacement buck from the 1970s. It is interesting to note that AC MkIV buck built by Brian in the 1980s looks significantly different, but that does not prove anything.