Besides the marriage record on familysearch, that is the only source I can find. They were married 20-APR-1863 in Philadelphia.
https://www.familysearch.org/ark:/61903/1:1:Q2WF-53PP
Also marriage record located here (pg 216):
https://archive.org/details/jstor-20086263/page/n9?q=%22samuel+gamble%22+pennsylvania+elizabeth+johnson+genealog
Would this be his son?
wikitree.com/wiki/Gamble-1999
Here is text where Samuel Gamble a mentioned a few times. As our the Morrow's and Johnsons.
https://archive.org/stream/historyoffrankli00bate/historyoffrankli00bate_djvu.txt
And another source:
SAMUEL GAMMEL (GAMBLE) Served as pvt., with Capt. Thos. Askey 1779- 80-81. He was of Fannett Twp., and his will prob., Feb. 1797. His wife was Elizabeth and he named sons Samuel; William; James. Daus., Jean Kennedy; Polly Morton; Shusana Elder; , Peggy Elder. Penna. Arch. 5th Ser. Vol. 6, p. 61, 393, 424.
http://portal.co.franklin.pa.us/WebLinkArchives/0/edoc/3230907/American%20Revolutionary%20Soldiers%20of%20Franklin%20County.pdf