I've been reading threads and noticed in one it was recommended to replace O2 sensors when rebuilding because they are hard to access when intake is on. I am doing a swap but not sure how to tell which specific O2 sensor is correct. Advance lists multiple upstream and I understand the difference in sides. But some are listed as "alternate 1" etc. So advice needed on the 02 sensor to order for '99 4.0 with EGR & low emissions, automatic tranny. I want to match my computer best I can.

Any other parts I should go ahead and switch also? Have new plugs, wires, Gates belt. Plan to order thermostat & PCV valve, plus new hoses for heater/radiator/etc. I have 2 sensors where my thermostat goes. Should I replace them too? New engine has 138K on it.

 

All Rangers 1986 to 2011 used the same heated narrow band O2 sensors

The difference in part numbers is the length of the attached wire lead and its connector
Bosch were stock brand

You can't get the wrong one for the computer(narrow band), just for length of attached lead or connector type to plug into the trucks harness