71/72 firewall holes

[cheyenne10]

I am getting ready to put a truck back together and swapping wire harnesses. Noticed that cabs at firewall block have varied holes for stock wiring. One has round hole approx 1.25" above square block with some harness thru it, 1 has 2 holes adjacent and outside the firewall block and 1 has neither of these. Do 4x4 cabs vs 2 wheel drive cabs vs 1/2 tons vs 3/4 tons vary in this area? If I end up ordering aftermarket wire harness instead of using stock harness swapped over what should I expect?

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