EXCLUSIVE

It's twue, it's twue ... it's reawwy twue ... James Deen's gargantuan penis IS the co-star in the Farrah Abraham sex tape ... at least according to James Deen.

Deen -- a professional porn star -- tells TMZ, "Word travels fast ... it isn't even edited yet. We shot it yesterday."

When asked if the two were dating, based on the fact they were seen holding hands yesterday, Deen said, "Definitely not dating. Got tested together on Friday and then saw her on set. That is my only experience with the lady."

As we first reported, the XXX footage is being shopped around to various porno companies -- including Vivid. We spoke to Vivid honcho Steve Hirsch who tells us he's seen the entire tape and says, "It's amazing ... and I'm doing everything in my power to get the rights to put it out."