Seth MacFarlane is one Flux Capacitor away from being able to travel back in time -- because TMZ has learned he's the proud new owner of an exact replica of the DeLorean from "Back to the Future."

Seth's people confirm the "Family Guy" mastermind purchased the DeLorean earlier this month. A source tells us Seth is having about $20,000 worth of customized equipment installed ... making it the coolest thing on wheels since the motorized bar stool.

One source -- who was lucky enough to sneak a peak at MacFarlane's unfinished DeLorean -- said the car already looks "insane."