I've got both versions of this kit; revell and italeri.
I'll post pictures of the boxes when I get home tonight.
I've a couple of these in progress as well and it's come to my attention that the engine in the 993 turbo is pretty much the same as found in the 964, with much of the newer engine being internal modifications. The only real departure is the turbo set-up and how the exhausts cross over to the opposite side.
In short, an enthusiast kit's turbo engine block is a good starting point for those wanting to do a more detailed kit...
Did you manage to source a set of Tamiya 996 Carrera wheels?
These, I'm afraid, are even harder to come by than the 993 Turbo kit it seems.
as for that pic:
it took me a while at first but Holy Hell!
I thought it was a drill/lathe bit at first but all I can say is wow.
Y'know, I'm expecting you to machine proper sized 993 Turbo wheels now; if only because I would like a set.
edit:
for those that are interested.