No power to ignition or dash

The two big wires that go through the bulkhead connector are the feed and return for the amp meter. The dash can be powered up by either one, since they are effectively tied together at the amp meter. It sounds like the fusible link was abandoned and the dash is getting its power through the return side.

If this is the case, as stated above, then there is no fusing on anymore to the main car power circuits and that is a formula for disaster.

Check your bulkhead connector. There are three high current wires that go through it that are often problems:
The amp meter feed
The amp meter return
Ignition power