Dear Mr. Glen Roach,
Thank you for posting your request on History Hub!
A search in the National Archives Catalog unfortunately did not render any results for maps of Williamsburg, Virginia, produced in the 1770’s, or close to the timeframe you're inquiring about. You may wish to contact the John D. Rockefeller Jr. Library at Colonial Williamsburg and inquire what they have in their collections. Please find their contact information here:
We hope this information is helpful and good luck with your research!