I honestly do not know much about Monroe County records, just that it's rare to find whole wills from early Georgia online anywhere.Wills can be long, and so usually what you find, if you can, is an abstract.
If you try putting "William Head" (with quotation marks) in the main search engine of Virtual Vault, there are three hits having to do with land (in the Georgia Colonial and Headright Plat Index).A William Head owned land in three counties way back.
I found a website that lists some Monroe County will abstracts, here:
If William Head had written a will in Monroe County and died there in 1835, you would expect his name to be in Will Book A, but I don't see it listed.There is a name to write to for abstracts of Will Books B, C, and D (use the link to get to that page).Maybe he was the W. H. Head in Book D.
There could be some clues for you in the Monroe County, Georgia USGenWeb website, here: