Good!
That black wire you traced with your finger was 12 gage or larger.
Did you notice the current went through just 3 connections?
1. At the stud on alternator - a ring terminal.
2. At the bulkhead - Varies, but usually a Chrysler type spade terminals similar to 'Packard 56'.
3. Main splice. Welded.
When everything is in good condition the only place there might be resistance to the flow of current is the bulkhead connection.