Oops, I forgot to fix the checksums. Just take the file I uploaded and open & export within PKHeX to have it fixed. (also attached a "fixed" one since I did it anyway)
Pokemon - FireRed Version (USA, Europe) (Rev 1).sav
Use PKHeX's encounter database to create one from template. Changing the PID/IV afterwards to something you prefer would require you to have a valid PID/IV in mind, which would require using an external tool to search for one.