You can make just about anything a twin with a little imagination. I have seen twins Sportster 60s, twin Dirty birdys, twin 4*40s, twin cubs, you name it. All you have to do is put a block on the nose and design the engine mounts and cowels for the wings. Doesn't take a lot and if you want to buy cowel instead of build them, get the cowel you want from Stans and design a firewall to match it.