Ginny, (and everyone with interest)
I called your mom already with this, but I believe I've found the birth record of the John Jordan you seek.

Listed under GORDON in Immanuel church records, in New Castle, Delaware. If this surprised anyone, just realize, water travel was more the norm and the river really only a mile wide if that ..New Castle is an adjoining county for all intents and purposes for Salem county. Plus there was not always clergy to be found for long periods in local pulpits. Not unusual at all to see folks on this side of the river show up in records of DE or PA.
Baptisms
John, son of John and Jane Gordon of Penn's Neck, June 8, 1759, aged 2 months, 25 days.
Sketch of Early Ecclesiastical Affairs in New Castle, Delaware, and History of Immanuel Church (Google eBook) p. 185
http://books.google.com/books?ct=result&dq=sketch+of+Ear...

The birth year is right from best estimates we have for John. PLUS his parents were already residents of Pennsneck, NJ at the time. That is nonspecific, so could be Upper or Lower Pennsneck, but something tells me they were already here. (near Auburn, now Oldmans twp, NJ).

Val