[patty442]

The line attached to the top of the differntial housing is not a breather. It is a return line from the differential cooler, which sprays specifically the pinion bearings with cooled differential lubricant. The exact location in your photo is a little off from oringinal but it will get the job done. Not sure what Kirkham guys think it should be but I have 6 original cast iron 427 competition diffentials, every ratio, which all have the a fitting tapped into the exact same spot on the upper portion of the cast iron Salisbury case above the pinion bearings. No need for shoulda, coulda, woulda, I assume, etc. discussion. That's what it is.