Having done a factory cloth harness rewire of and old a Sprite, and Painless kit rewires of a couple of other cars and race cars, as others have said the organization provided by a pre made was a HUGE brain saver, but all these were done on new installs, not a ‘need to run’ vehicle.
It is also a fact that any pre made likely might need modification.
While I can’t see loose wire build really coming out any cheaper at the end of the line, one thing you might consider is that a well chosen pre made harness has most of the crimping completed and fuse box connections predone and that is at a quality level worth considering since factory crimps and connections are difficult to reproduce outside a production setting.. that and the fact that the main runs are pre bundled and wrapped, which is also difficult to reproduce in the field and after the fact.
In any case do hunt down a very high quality crimp tool and the finest of crimp on fittings…….which local FLAPS around here just don’t sell.
