Basically any model of tractor in that size class is rebuildable an infinitum provided the chassis is still good. The selling price will depend to a great extent on what stage in the rebuild process the tractor actually is. For example it could be recently rebuilt nose-to-tail and therefore attract a pretty high selling price. On the other hand it might be on its last breath and need a complete rebuild, therefore the selling price ought not to be much more than scrap price....
I second Jerry's suggestion of widening your search to include the D8R because they have a bit more oomph than the N, on paper at least. Also they still are not all that electronic, and maybe the diff steer might be a bonus for you. Personally I don't like it apart from in certain conditions, but those conditions might just be what you're operating in.
Here's a link to the specalog for the D8R ........ http://s7d2.scene7.com/is/content/Caterpillar/C785813
Nige,will be mainly slot dozing.Wont be any scraper muck