keep eye open for a Eaton 22 series rear axle. found in F-700 and others. 80's and 90's
looking for 3.90 gears. These gears are large , The Ring gear should be 17 inches.
ring gear has 107497 on it 39 tooth
pinion gear has 107517 on it 10 tooth
Gears should also have the word eaton on them also.