A body 8 3/4 questions

You appear to have a bunch of useable parts. All the typical wear parts, like gears, bearings, etc, I would replace anyway, since you got the axle so cheap. Soak the whole chunk in solvent until you have reasnable assurance that bolts won't snap off. Check the spline on the axles to be sure its worth using. If not, axles are also easily found in the aftermarket.

You are going to put a bunch of work in this, do it right and go for the good stuff.