I am sorry to hear of your grandfather's passing. I hope the info I'm sending can help.
My father (b. 1930 in Conshohocken) had a cousin Harold from Conshohocken that he knew pretty well growing up and they were about the same age. The dates would be right for him to be your grandfather, Harold David Kriebel. This Harold had a sister Dorothy(now Swetkowski), and a daughter Marilyn (now deceased) and a son James who moved to Arizona. If I'm right, then your dad may be James (coincidentally, also my Dad's name).
There is a Harold Kriebel listed in Brecht's Genealogical Record of the Schwenkfelder Families, b. August 11, 1901 at 160 W. 7th Avenue in Conshohocken. Since this book was published in 1923, that Harold had not married yet and no spouse is given. My grandfather (also from Conshohocken) had a first cousin named Harold Kriebel. That and the dates seem to suggest that he was your great-grandfather.
Does any of this fit? If it does, please let me know and I can give you more information. Or if you have a copy of the Brecht book, it's under number 19-167 (page 259), George Henry Kriebel (father of the Harold in paragraph 2). Btw, if this is your family, we wuld be third cousins, once removed :)