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pyrogen007 said
I haven't decided on much, a modest radio w/ 4 speakers using the built in amp(no external or subs), keeping the factory A/C and everything functional and safe mainly, I know before I took the car apart the headlights dimmed/brightened depending on engine rpm and a lot of things didn't work that should have. Much of the factory wiring looked a little small for the current that it was expected to handle too.

I don't know what you're starting with other than a year that factory AC was available so prob '66 or newer.
You could do an engine compartment auxilery fuse/relay box for the A/C, Headlights, and maybe the new radio. It would be best to know how much power it can draw. Then you can size wires. Also some stuff is more sensitive to electrical noice than other stuff. One advantage of sending power through the battery positive junction is reducing noise. Disadvantage is that it complicates protecting against major shorts and monitoring the battery charging.

Some websites that can help with wire sizing are in linked in this post
In fact that whole thread is probably worth your time.

As far as the factory loads and wires, for the distance and time in use, they were generally adequate. Not much is really a high load. Headlights were # 6012 sealed beams until about '73. That's one of the more marginal circuits especially with the 6014 headlamps.
Battery recharging can be a high load, but for a short time the wires can take it. That's the main use of the ammeter - monitoring the load.
AC and heater blower on high are also can be over 10 amps, but OK for the normal length of time needed at high.
As mentioned, the factory did have heavy duty wiring options for high loads.
On the other hand they also added weakpoints at times. The connector at the steering column for '70-74 cars in particular and the engine connectors around '73 -'75? come to mind.

The weak points I see in repairs and mods tend to be poorly crimped or soldered connections, poorly supported and non-heat/oil resistant wires in the engine bay. If you're starting from scratch, there's probably some places you'ld want to use connectors with better sealing and more contact area than the old 1/4" and 5/16" push-on types. But the Packard series are adequate if properly made.