As far as CAs are concerned, there were no standards for conversion. Stens usually had their selectors welded in place, and either the trigger mechanism cover or trigger pin welded to discourage tampering. Some gas operated designs had their gas systems disabled, others had their trigger mechanisms altered. It really depended on who did the alterations, their ingenuity and mechanical skill. Some were so superficially converted that it was a joke.
It is doubtful if CA conversion systems and standards would be particularly useful for newly manufactured firearms, because basically there were no standards. Firearms that are newly manufactured would have to stand on their own two feet, as it were, and qualify as semi auto designs.
Look at the photos of the BD-38 mechanism that have been posted here. The trigger mechanism is quite different than the original (which never had a semi auto function). SSD designed a new mechanism that would fit in the available space.
For a different design, go to the semi auto Browning site, and look at the trigger mechinism used. It uses a combination of new and altered original parts. The resulting firearm is not a CA because it uses what is defined as a new receiver, which will not accept a set of original trigger parts.
Further examples are the Czech 58, 58L and 858. These use original receivers, which had never been assembled into rifles, and which were then altered to preclude use of selective fire trigger components. They aren't CAs, because they never were FAs.
