Questions of broadside tune identification are often complex, and in this case 'Over Hills and High Mountains' is really only peripheral to the matter in hand; so I won't quote full detail from Claude Simpson, The British Broadside Ballad and Its Music (New Brunswick: Rutgers University Press, 1966) where it is discussed in the sections devoted to Ah! Chloris Awake and Love Will Find Out the Way (pp 2-4, 472-474). Suffice it to say that the tune is lost, and the following brief extracts should cover as much as is needed here for now.

Having discussed the two alternative tunes named for 'Ah! Chloris Awake' ('a pleasant new Play-house Tune' and 'Love will find out the way') and printed what is probably the former, Simpson moves on to '"The West Countrey Maids Lamentation For the loss of her Maidenhead," a ballad licensed before 1685 beginning "Long time I lamented,/in sorrow and grief," bears the tune direction "Over Hills and high Mountains: Or, Chloris Awake" ( Douce II, 246 )' and concludes '"Over hills and high mountains" and "Ah! Chloris Awake" are interchangeable but probably not identical. No music for the former has survived, unless it is to be associated with "Over the mountains and under the waves," the first line of a ballad whose tune is commonly known as "Love will find out the way."' He adds a footnote:

'Chappell (PMOT II, 681-682), finding no music for "Over hills and high mountains," used instead the air "On yonder high mountains," which appears in several ballad operas, and which is strikingly reminiscent of the much older "Love will find out the way."

The entry for Love Will Find Out the Way includes music of 1651, and concludes

'The relationship between the tune of "Love will find out the way" and "Over hills and high mountains" is puzzling. The latter tune name is derived from the opening line of "The Wandring Maiden ... To an excellent new Tune" (B[agford] B[allads] II, 572); and this ballad is so evidently a paraphrase of the earlier "Truths Integrity" that one is inclined to wonder whether the tune for it was indeed "new," or whether its description was merely part of the advertiser's dernier cri psychology. We do not, at any rate, possess a tune called "Over hills and high mountains," although several late seventeenth-century ballads cite it for singing. Four ballad operas use a tune called "On yonder(s) high mountain," ^* for which no original words have been found; it bears a family likeness to the tune of "Love will find out the way," despite a good deal of difference in harmonic and melodic detail.'

^* 'They are Ryan's The Cobler's Opera, 1729, Momus turn'd Fabulist, 1729, Lillo's Silvia, 1731, all with music; and Drury's The Fancy'd Queen, 1733, without music. Chappell (PMOT, II, 682) used this music with one of the ballads calling for "Over hills and high mountains," but he recognised the lack of positive documentary evidence to link the two tunes.'