If you need to completely rewire your car the best way is to get reproduction wiring harnesses, you can get them from M&H or the Team Chevelle sponsor Ground Up. (Just click on the link at the bottom of this page) Ground Up will also have the ignition switch. A cheaper way is to use the Painless harness. However it is considerably more complicated to install.
Depending what has been altered over the years. The engine and forward lamp harnesses are often beyond repair. The dash harness usually survives in fairly good condition. It is the most expensive harness so I would try to salvage it.
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