Your Hiram has got to be my GGG-GF. However, I have his two wives as Harriet Pierce and Mary Bushong. BUT... I show Hiram and Harriet had these children:

Edward Mansfield Day
* William Oliver Day
Hiram Marshall Day
* Almira R. Day
* Mary C. Day
Lacy A. Day

...while our info doesn't exactly match up, it's too much of a coincidence.