The axle designations describe the style (banjo/drop-out/third-member/Hotchkiss vs. the one-piece Salisbury type w/ removeable cover), and the size of the ring gear in millimeters.
The C-designation axles are the Salisbury type. About all I'm aware of are the C216 used in the 1960's-era Patrol, and the C200, which has been used in all kinds of applications including the Y60 and MQ Patrol (also as a front axle), and on any number of small pickup/SUV applications, RWD vans, and even some medium-duty trucks.
The H-designation axles are the Hotchkiss type with the removeable third-member/carrier. Ranging from the little H165 used in some older RWD cars and vans, the H190 used in the Roadster/200SX and light-duty pickups and vans, the ubiquitous H233 used in the rear all sorts of pickups, SUVs (also as a front axle on the Patrol), and even large cargo trucks (there was a full-float dual-tire 1-ton version), the large H260 used in the rear of some Patrols and many cargo trucks, and the massive H290 used in 2+ ton cargo trucks.
There are also rear axle codes that describe the type of axle and approximate the gear ratio. For instance, the HG46 axle is an H-type, G designates the H233, and 46 indicates an approximate 4.6x ratio. See the link at the end for more on that.
Then of course there are the R-designation, which are the independent-suspension types from Hitachi. All are Salisbury-type with cover plates. The were used in the rear (R160, R180, R200, and R230) in scores of RWD and AWD applications. There are also front-end versions for 4WD IFS trucks/SUVs including the R180 and R200A. Subaru has also used the R160 and R180 for some time, the smaller Imprezza/WRX has R160, the STi has R180 used in the larger Subarus (Liberty/Outback).
Many of the internals of the same-size C-type and R-type differentials can be interchanged with minor accomodation.
Transfer cases, in addition to the older ones mentioned above, there are the following married transfer cases
TX10A: part-time, used in Pathfinder (1st-gen/WD21 and 2nd-gen/R50), Navara (D22), and pickup (D21).
TX12A: part-time, used in the Patrol/Safari. I'm not sure if the offset one used in the MQ is a TX12 variant or not.
http://www.uvc.co.jp/products/transfer/ ... sfer_e.htm
ATX14A: full-time, used in the R50 Pathfinder.
http://www.uvc.co.jp/products/transfer/ ... sfer_e.htm
That's about all I have for now. There's a good recent FAQ for USA axle applications here that would be worth looking at too:
http://nissan4wheelers.com/eve/ubb.x?a= ... 8310151411
Brent