Having scored a ratings knockout with its celeb boxing, Fox is now turning to amateur nude modeling.The net has pacted with Bunim-Murray Prods. to air “Girl Next Door: The Search for a Playboy Centerfold.” Two-hour spec will follow 12 women vying for the chance to take it all off in Playboy. Contestants will try to stand out sunbathing, primping for photo shoots, etc. The group, including a college student, a mother and a stockbroker, will be filmed at a Playboy-owned estate. Winner gets cash and her own spread in Playboy. There’s no airdate yet for the spec, though a May sweeps slot is likely. Fox reality topper Mike Darnell is supervising the spec for the network.