It would be much better to wait for motor installed and most all of the truck to be finished. There is nothing to gain to see if a new wire has continuity. Normally you don't pre-test a harness like it is for an aircraft or rocket. Our truck harnesses and install are low tech, straight forward, color coded, especially if it is a prewired fuse box type harness. One end is sort of already done. I reluctantly suggest wiring the lights portion and do some preliminary routing/planning, if you must have busy hands. Maybe dash/gauges. If you want further opinion, give harness brand, part number and vendor. State any added accessories, what motor and non stock items. Wiring is usually almost the last thing, after paint and all components are in place or ready to mount. Leaving seat out may help.
If a person is doing a refurbish, not a retore, same applies.
