http://www.academia.edu/7112520/Object…

I will try to find it, the piece was about the female gaze in Spartacus but it mentioned that all the male actors used prosthetics.

I read a PhD article written on it and apparently all Manu Bennett scenes are prosthetic as they need him to have a really big cock for the storyline.

Yeah, but those dicks are all prosthetics so not really.