Hello Tegan (Sharon)
I found the headstone for your grandfather James T. Inglis 1918-1966 at
St. Mary's cemetery, Plainfield, New Jersey. But it is a single headstone with James' name only. There is no other stone nearby with Elizabeth's name.
I have photo of James' headstone, but "attach a photograph" option doesn't seem to work for me

And I see you cannot attach to a PM. Any advice on how to attach photo would be helpful !
James' death record :
James Inglis, DOB 17 June 1918, SSN issued in New York,
last residence Piscataway (Middlesex County), New Jersey
Death date June 1966, age 48
Elizabeth's death record :
Elizabeth Inglis, DOB 3 Aug 1910, SSN issued in New York,
last residence Plainfield (Union County), New Jersey
Death date Jan 1986, age 76
Middlesex County and Union County are neighboring counties in Central Jersey.
Also you asked about St. Peter's Hospital in a previous thread... St. Peter's Hospital is in New Brunswick (Middlesex County). I was born at St. Peter's and grew up in South Plainfield (Middlesex County), so I know the area quite well.
Mary