MarSanZ:
Cool score. I just restored a "basket case" pair of AR-2axs, so I'm pretty well up on what you're about to get into. The results were so good that I'm now very, very interested in finding a pair of 3as.
First and foremost, I'd be concerned with whether the speakers are air-tight. AR's acoustic suspension depends on this. While your early cloth-surround woofers won't deteriorate like foam ones, they can still need a re-doping after all these years. Perhaps someone can chime in on whether ARs are prone to need resealing. There's lots of info here on how to do it, if need be.
Second, you're going to have to get a cheap soldering iron and get familiar with it if you haven't already. Removing and resoldering components in junk stereo equipment is great practice.
Once you decide to do some work on the crossover, draw yourself a detailed diagram of how everything's wired. You'll certainly want to replace the capacitors, using some decent quality caps poly or film caps like you'd find at Parts Express.
You'll also have to decide what, if any, of onplane's "Jerry-rigging" modifications you want to undertake. You may decide to take the tweeter's potentiometer out of the crossover entirely. You'll gain a much need 1 db in the high range doing this. The midrange pots have to stay in the crossover, though, or the mids tend to be too bright. Onplane recommends opening them up and soldering them permanently into the "full" position to avoid future problems.
You could also do what I did, and simply leave both old potentiometers in, but open them and carefully clean all the corrosion off with a dremel tool and a wire wheel. New potentiometers would be a great solution, but proper replacements are cost prohibitive and somewhat difficult to track down.
There's a ton of posts here that expand on everything I just said if you search around. Don't hesitate to message me if you need help. Congrats and enjoy one of the all-time classics.
