will these bindings work with my older leather Alico boots with the 3 pin system?

If it has a 75 mm duck bill on front and a ridge for the back of the binding to latch onto when you engage the "throw" (rear of the binding) then yes, your crappy not-stiff-at-all boots will work with this very stiff new binding.--aside from deleting the unnecessary slam on your intelligence that one of the previous responders threw in for no good reason, I've got to agree with James/Robert's answer, but it bears more explaining. This binding is way beefier than the old Voile's, and leather boots will have a hard time controlling it. In fact, your leather boots will have a hard time controlling any "modern" binding out there, and in all reality even old three-pin bindings won't make the leather boot any more effective--face it, you've got gear that should go the way of the dinosaurs. There is a very good reason nobody in their right mind skis on leathers anymore, just as there's a good reason nobody in their right mind skis on 210 cm, straight-ass skis (the setup that I learned on, oh, 15 years ago). GET SOME NEW GEAR! Seriously. You'll be happy you did, because plastic boots, shapely skis, and bomber bindings will give you CONTROL. Wow, can you imagine how much fun that will be?