I got an Orbiter 1.5 extruder and have been quite happy about it since. These days you’d be better off getting an Orbiter 2. As for the toolhead, there should be Ender 5 compatible mounts available on Printables or Thingiverse, if not you could design your own.

You can import a STEP model of both the Ender 5 and whatever mod you want to make to it and model your toolhead around it, that is what I did with the Mercury One project.