I just purchased a 4566 from a gun show and was told at the time it was a da only and I was really in the market for a 4506but have found them hard to get around here so I settled for the 4566. since owning it I have looked online and found other 4566's with a sa hammer, on the day I bought the gun while sitting with friends we noticed it looked possable to convert over to a sa/da gun is this true? and what parts do I need and where can I find them? thanx