BCPR's are jap spec ones, and refer to the height of the isulator on the plug. BKR's are ISO spec ones, and have a slightly shorter insulator length on the plug. Only like 2mm shoter, so it makes no difference really. The coil pack spring takes up the slack for the height difference, so both fit fine. BKR's are heaps easier to get here in Aus. Heat range etc is the same. Cause Skylines are jap spec, they refer to BCPR's in plug fitting guides.
I run BKR6E-11's gapped to 1mm, but have splitfires. With stock coils, I would run 0.8mm gaps, which is what i used to do with oldish stock nissan coilpacks to avoid 4500rpm misfires.