how much freedom do you have for this translation...?

how about "ready for use <mounting parts>" -> don't like "mounting parts", perhaps you can specify what kind of "Einbauteile" you are dealing with.

"ready for use" would suggest to me:
- it is in operating / working conditions (funktionstechnisch / technically functioning)
- it comes as a unit (i.e. fertig / assembled)

something like a "plug and play unit".

or am I just way off?

@ mrkh , thanks for your input. I fiddled around with your suggestions and came up with: operationally ready for use electronic components.