I don't see much for followup on repairs on this forum so figure I should pay back a little. I had to remove my front exhaust pipe to weld up a crack so I took the time to replace the O2 sensors. It is lots easier with the pipe out. I had read that the titania O2 sensors used on a range of late 80's Nissan Maximas would work on the later RRC. They physically fit, they are titania sensors, the three wire colors match and the SMP (standard Motor Products) SG130 is only $16 (w/shipping) on eBay. Yes you do have to cut off the Nissan connector and reuse your old connector. The housing does have NTK stamped on it too. I purchased my Rover (95 LWB) at 135K miles and I'm now at 204K, the O2 sensors I removed appear to be original, I would get a 44 or 45 codes if I let her idle more than 5 minutes when hot, and at $32 bucks why not. I purchased from eHerko (eBay) who also listed the NTK25016 for $52, which has the Rover connector and is Rover specific. The Nissan specific part I used has interchange numbers of SMP SG130, NTK 24007, Bosch 13021, and Denso 2343129.
I have nearly 1000 miles on them so far... no codes yet, last two tanks of fuel came out 15.3 and 16.6 mpg mostly interstate at about 65mph with some head wind. Runs well for an original 4.2L with over 200,000 miles. I changed out the plugs NGK BPR5EGP at the same time, Bosch Ignition wires and Lucas cap and rotor have about 30,000 on them. The plugs had 75,000 and the gap had opened to nearly 50 thousandths so they were due. Only issue I have right now is the Idle Air Control seems a little slow to respond at times.
Hope that is helpful information. Jon