Paul, Jeff''s right about the mounting frames but Scanmar is eager to provide a new frame suitable for your boat that will fit with the used Monitor product you buy. (They''re at www.selfsteer.com).
A good friend purchased a used Monitor a few years ago for his 40'' sloop but, after a Caribbean trip, has concluded he doesn''t use it enough to justify the investment. As of two weeks ago, it was still for sale. If you''re interested, email me at yahoo and I''ll forward it, putting you directly in touch with him.
We were docked in Trinidad near one another less than 18 months ago and it looked to be in very good condition at that time.