Just spent $254 at Year One on the reproduction Rear wiring harness (RL44) for the '69 Coronet Convertible.
All the wiring from the firewall forward is custom.
My Dash wiring is still the original. I will likely rebuild it with some custom modifications and modern fuse block, but my car is fairly modified.
If your car is mostly stock, it is alot easier and takes less time to install the M&H Pre-Made harnesses.
When We wired Mikes car, that was all custom stuff, Dash, EFI, TCI 6X Transmission, and more, He started with a Ron Francis Kit, and by the time we were done likely had around $1,000+ into the wiring kit and all the extra wiring, terminals, and looming. Not to mention over 500 Hours labor building and installing the custom wiring harness(s).
Just saying, the M&H Wiring harnesses may appear expensive, but the savings is in the install time, and not having to source all the different wires, connectors, terminals, light sockets, loom, heat shrink, tape, and the tools (crimpers, strippers, and such)
1970 SuperBee Rear wiring harness ($188):
https://www.yearone.com/Product/chrysler-b-body/rl52