Though I cannot help you with the location of a gravesite for William and Mary ? Finton, I can provide you with an overview of John Finton of Romulus, who was named as an executor along with Reuben Smith 2nd of Hector, for the last will and testament of Mathias Swegles.
I noted that you had some children listed for John on your public member tree at Ancestry -- not sure of the source for these, but they differ considerably from other records I have found. Some of John Finton's children are documented in his Revolutionary War Pension file, at least those who were living as of 1851. Others are noted in DAR lineage records and deeds.
John was listed in DAR records as having wed at least twice: 1. Phebe Wells and 2. Elizabeth Roberts. Seneca County deeds suggest the possibility that he married again after the death of Elizabeth in 1821.
From what I can determine in Orange and Seneca County records, John and Elizabeth married, say 1783 in Orange County. Their children were: Ann, Phebe, William, Amy (my ancestor), Esther, James, Asa, Emily, Alva and Josiah J. Of these children, Ann, Phebe, William and Emily were not living as of 1851. William died in 1846 at Hector, Emily in 1823 at Romulus, and I have no record of Ann or Phebe. By his first wife, John Finton had: John (died ca. 1815 and his widow and children moved on to Ohio), Elijah (still living in 1851) and Mary for whom I have no further information.
I note that you mentioned Wyckoffs in one of your Swegles' posts. Amy married first to William Wyckoff, second to Jonathan Swarthout, a widower. Esther married John Wyckoff. John and William were brothers, children of Joseph and Keziah Foree Wyckoff of Romulus.
Is there another source besides the cemetery marker of Amy Finton Swegles for the names of the parents? I have found no other proof that Amy and John were related except for the mention of John as executor of Mathias' will. He was described as "trusty friend." Amy did state her relationship to Joseph in a RW pension affidavit.
You can find photos of the gravesites of John and Elizabeth Roberts Finton and some of their children online at www.findagrave.com
. The SAR recently replaced his marker, which was broken off. They are buried in Kendaia Cemetery on the grounds of the former Seneca Army Depot.
John and Elizabeth Roberts Finton were active members of two Baptist churches: one at Slate Hill in Orange County. John's name is on the deed for this church. After they relocated to Seneca County on or before 1804, John was an elder at Kendaia Baptist Church.
As for place of birth, John Finton stated in his RW application that he was born near Deer Park 8 May 1752. This is near Port Jervis in Orange County. John died at Romulus, Seneca County 14 February 1839.
Please contact me by email if you have questions or would like more background information on this family.