Your probably better off with the 7x10. Has the same swing, your really only losing a couple of inches of length, which if this is for flashlight stuff your gonna run into shortcomings with the bore size before you have an issue with length, that was my experience with my 7x12 anyway.
The rust on the chucks of the 7x12's not really an issue, it doesn't look like its on the jaw faces where it would affect clearances, but the ways look pretty rough from the pic. Seemed a little high to me, but it did have a quick change tool post.
You'll find tons of uses for it, mines one of the more used tools in my shop, congrats on the score.
-Michael