Does this diff look normal? Specifically, the area pointed to. I'm considering buying it.

 

Yes, that's a diff from a 4 cyl truck and that divot there is where the dowel pin goes in to hold the cross-pin in place.

 

cool. that's the answer I was hoping for. thanks for the reply.

 

When checking the diff, the ring (big) gear should spin smoothly with a little resistance. When you rock the ring back and forth, it will make a tiny "clack" when changing directions, you should barely be able to see the play that accounted for that noise as its should be about 0.01" for a used diff. Make sure the faces of the gear teeth are smooth as well.