What do I need and what do I don’t!

I have a 1975 scamp 318 backed with a 904, I am running my ignition system with a MSD 6A box, that being said nothing really electrical works on the interior of my car except the radio.

My question is what wiring under the hood can I get rid of and what do I need to keep? The original wiring harness is hacked up and basicly junk!

I have aftermarket fuel, tach, oil gauges. I really just want to clean the wiring up and not have such a rats nest!