Unfortunately that doesn't look good for disassembly today.
I would clean it really well after first cutting the chains off, then spray the life out of it with PB Blaster, and walk away for a week respraying it as I passed it daily, then knock the roll pins out, if you can get it running, then hit the sprocket teeth with a wire brush and put new chains on it ( I know, that sucks) , now drive the heck out of it trying to get the sprockets free of the axles ( to get the last few loose (you may need to re pin the free ones). Now the fun begins as you will have to free the lock collars from the bearings and get the inner bearing free of the axle, once the bearing is off the axle you can remove the 4 outer bolts from the outer bearing flange and attempt to pull the axle (you may have to sand the inner portion of the axle to get the sprocket off the axle) then you can remove the outer bearing out of the machine. Then again maybe it will just easily come apart and all this be moot, Maaybe.
Now that I've scared you, ( if all 6 axles are the same length) the easy, yet expensive , way is to cut the axles out and replace it with the new hd axle and splined sprockets with the 1 inch inner and 1-1/4 outer bearings with new double sealed flanges or the 72mm hd bearings.