An alternative to the bulkhead repair is not using it for the alternator and battery feeds. Run those wires straight through the firewall using a grommet. Shown in the diagram below originally from NachoRT.
8 gage wire is probably overkill for your situation. With 10 or 12 it will be easier to make good connections.
Last edited by Mattax; 09/05/1701:37 AM. Reason: add comment on the 8 gage