Don't have Bob Woods contact, but I think it's on a post up in the transaxle forum. I believe Olthof uses Quick Time's steel bellhousing. Quick Time is U.S. made and have their own website. I've got one on my SPF. It may be slightly heavier than an aluminum one, but is smaller in diameter. It has the nice advantage of being able to unbolt the transaxle without removing the bellhousing from the engine.