This may be an issue with his later harness (57) this is my third re-wire using AD specific harness kits and I just don't see it as being that difficult. If you want to never mess with it and eliminate most issues prep for it.
Use your original metal instrument light pigtails (they don't pop out).
Heat shrink your connections and terminations.
Add a small modern blade fuse panel for additions and fuses (mine is hidden under the dash).
Tie and support the wires at the factory locations and any others where you suspect an issue may arise.
With a bit of additional thought and effort it can be made into a very robust installation.
