For BioD or WVO, buy viton seals from McMaster (size 111) and get a new return line kit.
Like this: https://www.rockauto.com/en/catalog/ford,1988,e-250,7.3l+445cid+v8+diesel,1114388,fuel+&+air,fuel+injector+hose+repair+kit,11219
Also, if you really want to use braided fuel hose, make sure...