The deal on the bulkhead connector is back assward. By running straight to the battery your eliminating load that would normally pass through the bulkhead connector thus eliminating heat and stress on the old crappy set up.
Do not kid yourself. Relays ALONE does not cure this. Whether you rob power from the alternator stud or from the starter relay, "at some point," high current is still going through the bulkhead, UNLESS it has been upgraded / modified, or at the very least brought back up to "as new" standards.
Even Ma knew these were inadequate-----look up what is know as "fleet wiring" sometime. Essentially, this is very similar to an ammeter bypass, except that it runs new / larger wires through separate grommets, to relieve the bulkhead connector
These type connectors are the same essential type that are commonly used in household electric furnaces--at a nominal 20A of current. They fail "all the time." One of the checks you do when servicing a heat pump / electric furnace is to inspect the electrical connections. I've replaced dozens in the years I did this service work.
