I've just been reviewing my mother's will and have been given a salutory reminder that any historical will that I find may be a very misleading document!
My mother's circumstances changed drastically between making her will in 1979 and dying in 1987, with the result that none of the bequests in her will were actually fulfilled. (And I should know — I was her executor).
I wonder how many historical wills in my family were similarly not executed as expected, in part or completely, and how I could tell. The "Death Duty Registers" kept between 1796 and 1903 could help in England and Wales, if the estate fell into the category where duty was payable... and if the registers for that period have survived. The National Archives hold the originals; that link also leads to some useful research guides on the subject. Findmypast has the indexes online.
Other than that, I might find court records if there was a dispute about the will. Or there might be an itemised and valued inventory of goods with a will or probate document that could show how likely it was that the estate was sufficient to cover the bequests.
And now I'm going to ask a question on Genealogy.stackexchange.com to see if anyone there has suggestions I've overlooked.