I have a 1978 2wd F250 with a D60 rear. I'm looking to replace the seals, but several of the application or fitment notes I see on parts state that the part is for a front inner seal.

Is there a difference between a front D60 seal vs a rear D60 seal?

 

Yes there is, the front axle has inner seals in the center at the differential, just out board of the carrier bearings, the rear axle has seale in the wheel hub itself.