Hugh Shannon Family of Gaston Co., NC

This family is well documented from 1790s to present.Hugh Shannon (?-1783) is the pioneer ancestor in NC.Tradition is he came from Mercersburg, PA area.Land records in Charlotte, NC verify he purchased 600 acres in present day Gaston Co., NC on Nov. 24, 1763.
I can't link him conclusively to Shannons listed in PA.Believe he might be son or nephew of William & Mary Shannon who died before 1741 in Sadsbury Twp., Lancaster Co., PA.Believe he migrated westward to Carlisle-Cumberland Co., PA area before heading south to NC.Have hit a wall in tracing ancestry beyond Hugh Shannon.Anyone know anything about Hugh Shannons in PA prior to 1763?Many thanks.