Replacement wiring harness

The under-hood wiring on my 70 swinger is complete garbage. Bulkhead connectors melted wires melted,spliced, hard as a rock etc..My fuse box is corroded but the rest of the underdash stuff seems "ok".
A factory replacement style harness is not in the budget and really it wouldn't make sense as I'm planning on running an HEI distributor,electric fuel pump,electric fans,one wire alternator,composite headlights with hid's. So I'm looking at all the different "universal muscle car harnesses" but I'm not sure how to make them work with the factory instruments which is a must. Also I'm on a super tight budget so name brand stuff seems out of the running.
Does anyone have experience with some of these no name universal harnesses? I assume they are more geared toward GM stuff.
How do you make factory chrysler turn signal switch,ignition switch and gauges work with these?
Im looking at something like these but I'm open to suggestions.

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https://www.amazon.com/dp/B01M7U30VD/?tag=joeychgo-20

I'm probably over complicating things but I haven't wrenched on cars in twelve years and I haven't had any electrical classes since the mid 90's.
I was tempted to pull the underhood fuse box out of one of my ram parts trucks and attempt to make my own harness but that seems a little daunting as well.