68 Dart wiring questions

No it won't. Only battery charging gets bypassed with a direct wire. Current still needs to go through one or the other feed at the bulkhead to run everything else. How well this works depends on the execution. It also leaves the operator without a way to judge system operation. So then a voltmeter is needed.
And without a fuse or fusible link, a short in the alternator will be a serious burn. Now with two fusible links and two paths, a short will burn twice as long. All for what? Sometimes there is a reason, but most the time people are best off just finding problems and fixing them. That's difficult enough for someone whose not done it before. How many tmes do we see people post correct splicing, crimping methods, tools and connectors? How many more times do we see the cheapest closed barrel terminals badly crimped with conductor exposed, etc?

For a long time I was pushing a headlight relay harness as a win-win for reducing loads on the main feeds going through the firewall, the headlight circuit, and improving the headlight power. But with Rob not making them at the moment, I don't know of off the shelf good ones to recommend. Dan Stern sells kits with quality parts, but its project that has to be done reasonably well.