I don't have knowledge of any William Harrell born in 1900 that was in FL area.

Nearest to yours born in 1913 GA died in 1968 MO, and he may have served some time in FL with Army. His name was William Lewis Harrell, II, Sr, since he named after his GDad and has son named after him, being III, Jr.

William Harrell born 1776 (my 4 Great Grand Father by my mom and 3 Great Grand Uncle by my dad) who was brother to Levi Harrell, II born 1777 (My 3 Great Grand Father by my dad and 4 Great Grand Uncle by my mom) (since their father Levi Harrell, I, was my 4, by my dad, and 5, by my mom, Great Grand Father).