While I'm sorry I don't have information on William, I do have a Quaker Dean line as well - they could be connected?
My line goes from Phoebe Titus Dean, my g.grandmother > Daniel Dean Jr (b.1793 Cornwall, Orange, NY) >Daniel Dean (b.1743 Belleville, Essex, NJ) > Jedediah "Jorsey" Dean (b.1720 in either New York or New Jersey).
After Jedediah I'm a little confused, as there is conflicting research on the internet, and I live in Vancouver, Canada!
I understand that while my gg grandfather, Daniel Dean, and his wife Abigail Carpenter were Quakers, Jedediah Dean attended the Methodist Church.I'm not sure if Daniel Dean Sr or Jr was the first to join the Quakers.
Wonder if you've found any more info on your William Dean?
There is also a Hicks connection in my Dean family, as a gg aunt, Ann Davis, married Lorenzo Dow Hicks, but divorced him when he joined the LDS Church.