More info from Brent...
Learned a few things yesterday...
I'm not sure that the A in R200A etc. indicates an offset diff, from what I gather, it indicates a short-pinion diff. The Patrol uses offset front (and even rear) H233 diffs, but they're not designated H233A. I have seen in the Nismo catalog that the R180A was developed with a shorter pinion (by 120mm) to reduce driveline angles vs. the regular R180.
The R180A axle designation is RB
The R200A axle designation is RC
C200 and R200A gears ARE INTERCHANGEABLE. Yes, the same part numbers are used for the same ratios in the Nismo catalog for both diffs.
Best I can tell, 10mm ring gear bolts were phased out of the H233B diffs 6/86.
There are 5.571 and 5.875 gears available from Nissan/Nismo for the H233B