I used a Bosch O2 sensor (for Ford Mustang) in my 740 Volvo and spliced the wiring harness. I had trouble soldering one of the wires. It seemed to be made of stainless steel or something and the solder would not bond to it. I ended up crimping the connector on.

I carefully compared the Mustang part with the original Volvo part and except for the wiring harness, the parts are identical. INHO it is well worth the 10 minutes it takes to splice the harness and save $80 or more.