You're well on your way.
I recommend replacing that parasitic fan with a clutch fan (easy option) or electric fan (more complex option).
Also, when I put headers on my Monte Carlo, I ran the positive battery cable along the oil pan rail and out by the fuel pump, to avoid any accidental contact with a hot header primary. I had to get a longer cable. I thought I posted the pictures here, but don't see them.
With my new headers, Hedman recommends routing a longer battery cable through the motor mount. I have my battery in the engine bay and have no interest in moving it to the trunk. Has anyone else run the battery cable through the motor mount or some other pathway to the starter? It is clear that...
maliburacing.com
I was able to find an NOS GM battery cable that was the right length. I don't remember the exact length, but 54 inches comes to mind. I added some clamps to some oil pan bolts to keep it in place.