John uses Delphi Metri-pack connectors (the same as GM) for most harness connections. They are easy to assemble and crimp, and easy to connect and disconnect when complete. For bulkheads (no grommets allowed in Unfair!), he uses Molex XRC connectors. They are very similar to a mil-spec connector, but are about one-quarter the cost, use a more traditional crimp, and can be disassembled when you make a mistake. The key to using bulkhead connectors is keeping track of every single wire, and writing it all down in a table that can be referenced by wire color, connector location, and intended purpose. Amperage ratings are important to factor in as well: the XRC connectors are rated to 14g wire/13 amp current. Higher current needs will have to go through the more traditional large bulkhead connector that can carry 10g wire and 40 amps.
Grouping wires together in visible locations (like under the hood) is traditionally done with wraps of wiring tape or split loom plastic tubing. Those are ugly and bulky. Instead, John uses nylon mesh held in place with shrink wrap. It makes for a tidy and flexible way to run bundles of wires together, without having to use tie wraps every 4-5 inches to keep individual wires from drooping out of the harness.
As we said, this won't be about connecting the gray wire to the yellow wire. Instead, follow along as John shows off some of his techniques for building a safe, reliable, and easy to service wiring harness.