I did mine last month at 83k miles. I replaced the tensioner, idler and water pump while I was in there.
-1999 Mustang GT 5 speed- Mild Mods-SOLD
-1994 Exploder Winter Beater-SOLD
-2003 Sonic Blue SVTF ZX3 Build #800 of 3,985. -SOLD
-1998 Mark VIII LSC Collectors Edition #592
-2001 Mustang GT 5 Speed