Check out Hither Hills State Park.. There is information (pamphlets) at the trailhead and parking area.They are pretty much only fire roads, some of them get pretty rutted out and some pretty deep water/mud crossings (alternator warning) but nothing difficult.. Otherwise Beach driving is all you are going to get, afterall you are on AN ISLAND...
Paragon Adventure park is a pay t play offroading park in Pa. I80 & I81
paragon website About 2 hours from manhattan.
And Rausch Creek is another pay to play offroading park in Pa. off of I78 and I81.
About 45 minutes south of paragon
rausch creek Good luck..