Advanced Adaptors makes them but Speedway Motors is my choice for purchasing. I tried to go from Advanced Adaptor website for the parts but seems they may be to busy supplying large retailers instead. Waited a month for the setup and when got tired of waiting called and they still were not ready. Canceled, ordered from Speedway and had it three days later. Got two carbs from junkyard for 20 bucks, gathered my brass collection together and started building. It is runnning off the single carb right now, not tuned for the dumps. It's hard to get the seconds to kick in in the driveway ; ) You got to see the breathers, more the process of mocking up than the breathers thmselves I guess.
I have been playing with cans on top of the breathers for weeks and decided on pair of mixed nut cans from walmart for the mockup. Took 'em to FLAPS and said I want breather(s) this diameter and filters this size. They found them! Pickem up in an hour. Will try to post a picture or two this afternoon.
Brett