Source for Good Electric Components

For well built fuse blocks at reasonable prices it is hard to beat OEM stuff. Visit your local pull apart and see what fits your needs. When I upgraded the electrical system on the 83 D150 and the 68 Barracuda I used power control modules out of mid 90's Dodge Caravans. Nine relays, six maxi fuses and 10 mini fuses in one box. You will need to spend the time getting familiar with what ever box you choose to understand power in and out and ground wire routing. I knew I was doing two vehicles so I got three identical boxes from the pull a part, so I have one extra for a reference. Spend the time un wrapping the OEM harness and get a foot or so of each wire, you then have a good lead to splice to. I also made a drawing of the wire routing in advance so I could plan the install and have a guild for troubleshooting.
For terminals, wire and relays, there are multiple sources on line. I would not worry too much over off shore content. The computer you are using to post with has major components that were made off shore and it seems to be working for you.
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concerning wire selection, it is important that you understand and properly size the wire. Too small and you risk overloading the wiring harness, too big and you end up with a bulky and hard to package wiring harness.

You will need a good reliable crimping tool. I crimped then soldered then covered in marine shrink wrap all of the electrical connections.

I cannot overstate the importance of having a detailed plan, drawn out so you have a guide to go by and a method to trouble shoot with.