I used an after market K&N filter from the local auto parts
store. They are cleanable and last for life(?.) I do not remember what it's application was but it fit right over the intake manifold in place of the silly thing that is there originally. The K&N filter is about 6" in dia. and about 8" long with an inlet at one end. I later attached a length of exhaust
hose to the intake manifold and moved the filter off to the side about 2' to free up some space around the engine. The only problem with this project
is dealing with the engine breather connection. I moved it to the K&N filter body with a length of hose and a hose barb fitting.