Sorry it's taken me so long to get back to you. We had a little family emergency and I fell behind on my genealogy!
Anyhow, I'm sorry to report that I didn't find the James Phelps you were looking for. I don't have many books that cover Muhlenberg Co. or the surrounding area.
My suggestion if you haven't already tried this is to write to the Muhlenburg Co. courthouse and see if they have any marriage records dating back that far. Give them the names you are looking for and an approx. time frame. Include a SASE so they can respond easily.
Muhlenburg Co. Courthouse PO Box 525 Greenville, KY 42345
You might also try: Muhlenberg Genealogical Society PO Box 758 Greenville, Ky 42345-0758 There maybe someone there that can hep you out.