I received this information from a Rhoda (Lucas) McCurdy researcher.Unfortunately the researcher Marilyn passed away about 10 years ago.She was descended from Mary McCurdy & William Bowman - William, I believe, a brother of Calvin.In the 1860 census, Calvin & Rebecca Bowman and William & Mary Bowman are on the same census page of Porter County, IN.
Rhoda (Lucas) McCurdy dates are b: Oct 1807 and d: Mar 1845.This Rhoda was born in Warren Co. OH. Thus John & Rhoda cannot be the parents of the Rebecca McCurdy whom you seek.John McCurdy (Rhoda's husband) remarried and had a second family but in 1860 census there is no Rebecca in household.
Mary & Rebecca's brother was Francis McCurdy.If you feel strongly about this McCurdy family, you could check out Francis??In 1870 he had a family but no Rebecca?
Mary & Rebecca's brother, John Nelson, was written up in the LaPorte County History and mentioned he went into business with his older brother, Francis.