Systems and methods for implantable medical devices and headers are described. In an example, an implantable medical device includes a device container including an electronic module within the device container. A header core includes a bore hole portion and at least two electronic connection features disposed within the bore hole portion. The bore hole portion includes at least one cavity configured to allow placement of at least one of the electronic connection features within the bore hole portion. The at least two electronic connection features are electrically coupled to the electronic module within the device container. The header core is configured to allow location of the at least two electronic connection features in a selected configuration within the bore hole portion. A header shell is disposed around the header core and attached to the device container.
