As far as a 90 degree elbow, you can use an intake off of a verticle shaft engine, it has a 90 degree intake. With that you may be able to get a side draft carb on it.
EC does build the carbs for the opposed engines. I have been looking for awhile and haven't found anyting thats a direct bolt up.
These engines are made to run rich, you want a fuel pump. They do not cool well and will overheat quickly if run lean.