The Saito 100 and 200 Vee twins have left cams in the front half of the engine. Some of the flat twins use left handed cams. But I'm not so sure this will work?

But to make the engine look like a mirror image, you have to use the reverse cylinder like is on the front of the V-twins or the left side of the flat twins. They have the intake and exhaust reversed. But you get into a problem mounting the carb.

I don't see it as a cost effective alternative to change the cylinder. In other words, it'll cost more than you will want to spend if you want the engines to look like opposites.

Enjoy,

Jim