Us in the USA use an average "pump" octane spec (by law noted on pump, look) of MON+RON/2. Motor Octane Number and Research Octane Number use different methods to establish the octane rating. Typically MON is quite a bit lower (numerically) for a given blend than RON. European cars almost always specify RON for their octane ratings (especially the older cars we love).
87 "pump" octane should be OK for a normal B18B at any kind of elevation (with no head or block "skimming" or overbore). "Plus" may be required in hot, low elevation, towing, high performance applications or if the engine has been rebuilt.
Interestingly, since the thermal cycle for internal combustion is more efficient if you can run a little hotter combustion temps, polishing the combustion chambers and knocking off any sharp edges can give you some additional "resistance" to knocking under otherwise identical conditions (ceterus parabus).
Mike!