Dana 70 spindle threads

To replace my Dana 70 I bought a single wheel one that was supposed to have come from a Chevy (the BOM doesn't lead me to any identifiable one). The more research I have done and the unique to Ford spindle nut leaves me thinking it's a Ford.

The question I have is on the threads. When taking off the stock spindle nuts one of them was really really hard to get off. It fought me the whole way and I noticed when I finally got it off there were about 2-3 threads on the end of the spindle that were messed up. My thoughts were to get a fine file and try to clean them up some or grind off the first couple of threads and not worry about it. I was wondering if anyone had ran into this before and knew any tricks.

I found something called a thread chaser (never used or seen one before so new to me) that worked like a charm. I ended up finding new spindle nuts at napa for $15 a piece that were nylock washer type.

Best I can determine from buying parts for this rearend it is around a 79 Ford F350 rear and not a chevy as I was led to believe. It is a 70 HD from what I can tell as it has the 35 spline axle shafts. The tubes do not taper down at the flange either.