Does the spare axle housing have a good 3rd in it? I didn't catch that part. What you just described would probably be the least down time for any vehicle. You'll need to figure the brake line stuff though.
60 series arms makes everything easier with your current 60 setup. You just buy a set of 60 tres and if you have 70 series drag links/tie rods/relay rods or whatever you want to call them, it all bolts up