Mystere's are actually still being produced and sold (supposedly)... See the recent posts in the Mystere forums. I dont know about the 4.3's but i hear the 5.5's and 6.0's are.

I just purchased and received parts from them (upper rudder castings). I can't say it was fun, easy, cheap or even correct.. but i got the castings (still waiting for the adjusters that were paid for with them, and they were not anodized as i expected)