The O2 sensor isn't used during warmup. It's disabled until the coolant temp is up. Not a bad idea to replace it.
Save some bucks and get a pre-cat 4-wire universal for a Ford modular V8, Mustang, EconoVan, F-150, etc. They're the same except for the wiring plug, just cut yours off & splice them with a bit of solder & heat shrink tube.