An implantable medical device comprising: a device container including an electronic module within the device container; a header core (2220; 2320; 2520) including a bore hole portion (2232; 2332; 2532) and at least two electronic connection features disposed within the bore hole portion (2232; 2332; 2532), wherein the electronic connection features are selected from the list consisting of a connector block and a tip connector, the header core including at least one cavity (2234; 2334; 2534) configured to allow placement of at least one of the electronic connection features within the bore hole portion (2232; 2332; 2532), the at least two electronic connection features being electrically coupled to the electronic module within the device container, the at least two electronic connection features being configured to engage with a lead disposed within the bore hole portion (2232; 2332; 2532), wherein the header core (2220; 2320; 2520) is configured to allow location of the at least two electronic connection features in a selected configuration within the bore hole portion (2232; 2332; 2532), wherein the at least one cavity (2234; 2334; 2534) is formed through a side of the header core (2220; 2320; 2520) and intersects the bore hole portion (2232; 2332; 2532) so that the electronic connection feature can be inserted into the cavity (2234; 2334; 2534) from the side of the header core (2220; 2320; 2520); and a header shell disposed around the header core (2220; 2320; 2520) and attached to the device container, wherein the header shell is molded around the header core (2220; 2320; 2520) and molded to the device container thereby attaching the header core to the device container. a device container including an electronic module within the device container; a header core (2220; 2320; 2520) including a bore hole portion (2232; 2332; 2532) and at least two electronic connection features disposed within the bore hole portion (2232; 2332; 2532), wherein the electronic connection features are selected from the list consisting of a connector block and a tip connector, the header core including at least one cavity (2234; 2334; 2534) configured to allow placement of at least one of the electronic connection features within the bore hole portion (2232; 2332; 2532), the at least two electronic connection features being electrically coupled to the electronic module within the device container, the at least two electronic connection features being configured to engage with a lead disposed within the bore hole portion (2232; 2332; 2532), wherein the header core (2220; 2320; 2520) is configured to allow location of the at least two electronic connection features in a selected configuration within the bore hole portion (2232; 2332; 2532), wherein the at least one cavity (2234; 2334; 2534) is formed through a side of the header core (2220; 2320; 2520) and intersects the bore hole portion (2232; 2332; 2532) so that the electronic connection feature can be inserted into the cavity (2234; 2334; 2534) from the side of the header core (2220; 2320; 2520); and a header shell disposed around the header core (2220; 2320; 2520) and attached to the device container, wherein the header shell is molded around the header core (2220; 2320; 2520) and molded to the device container thereby attaching the header core to the device container.