As already mentioned, the lc-1 can be installed in the stock location and configured to simulate a narrowband signal to the ECU as well as supply wideband output to a gauge and or another sensor input to tie into dsmlink.
I've never done it as it's more work to setup. The easier route in my opinion is to leave the front sensor alone to do it's thing and install the wideband o2 sensor further down stream. On my 2g I installed It in the second o2 sensor location post cat and didn't have any issues. On the evo I welded the supplied bung to the end of the downpipe pre cat. No problems. Every dyno I've ever been to stuffs a sensor in the downpipe... I don't think location matters.
I've never been concerned with sensor accuracy due to placement (never seen an issue installed in any of the above mentioned locations). As long as there's a consistent reading to use, you'll be fine. Fix any exhaust leaks too. /ubbthreads/images/graemlins/tongue.gif