[aoncurly]

Your idle hunting symptoms are identical to what my 81SC had. For me, it was a bad O2 sensor. You said you replaced the O2 wire, but what about the sensor itself? After replacing the sensor and readjusting the mixture, the idle was fine.

Was the O2 wire replaced at the loom end where the plug (on left side of engine compartment, not at exhaust end) is? My understanding is that wire is shielded and can be difficult to splice correctly. Although not related to the hunting issue, I also had my plug end connector replaced as it was crumbling, and my mechanic said splicing the wire was very difficult. He had to cut into the loom to properly connect the new plug. The crumbling plug and wiring caused other mixture problems, like surging and just general bad running. After replacing that, and readjusting the mixture, my engine ran much better.

Good luck.