Those three piece rims are why I made the boat anchor comment in my post above. Unless you are going for full authenticity, there are much safer alternatives for yourself and whoever mounts your tires.
If you are dead set on using them, (they aren't called "widowmakers" for nothing), make sure your tire guy uses a safety cage or retainer straps or chains while mounting or demounting the tires. If he doesn't, take them to someone that does.
