Rally dash redo

Still futzing with it. Undecided/unsure what to do with this circuit. This is one of the splices. Sorry for amount of pics, just trying to give a clear picture of what it is.
All wires in good shape EXCEPT, some are very stiff. Especially the black 12 gauge that goes to ign switch. Not stiff in the middle only at ends. Also black 14 gauge that goes to fuseblock(again the ends). Welded splice feels solid.
When I can/need to I have upsized 1 wire size to "better" the harness. This factory splice has 5 wires and range from 12ga-18ga. The 2 black are the "worse" of the bunch. Shouldn I replace with original size, or should I step up a size for each of these 2? If I step up that means 10ga running to ign switch and 12 ga running to back of fuse block. Tight fit??
Pics of all 5 wires and labels.
Thanks
Steve

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