The codings were done to match chassis designs. Like most manfacturers Nissan uses a few diferent types of engines and adapts them to several chassis designs in most cases only changing engine mounts. The codes are chassis codes. The codes are not as easily explained as you would think but basically though the B13 or FB13 was the designs you guys would be familiar with in the 1991 to 1994 Sentra which is the same chassis and body design for the 1991 - 1994 Sunny from Japan. Here is where it gets tricky, this same design in Mexico goes from 1991 to 2009 and is called a Tsuru. The N series chassis was what was found in the Pulsar (I think it was called an NX in the US). In some markets the Sunny and Pulsar names are switch on some chassis models...go figure. Major design changes to a chassis resulted in a new code hence the B13 B14 B15 etc.
The JDM B13 Sunny had several engines GA13DS, GA15DS, GA16DE, SR18DE and there is a CA series as well and there was talk of an SR16 but I dunno about that one. DS were carbureted whle the DE werefuel injected.
B14 in the US started around 1994 to about 1998 with the shape change and some sport models were badged as 200sx. The corresponding JDM Sunny had some trim differences but were essentially a RHD version of the Sentra.
Here in Jamaica we tend to get a lot of JDM cars so we tend to see a lot of the Japanese names and trim.
Nissan Sunny - Wikipedia, the free encyclopedia
Nissan Sentra - Wikipedia, the free encyclopedia
List of Nissan engines - Wikipedia, the free encyclopedia
The US version of the B15 onwards is a completely different body design from the Japan version.
In a nutshell pretty much all the info for the B12, B13 and B14 are easily transferrable from US Sentra to JDM Sunny bearing in mind some differences are evident. One notable one is that the JDM B13 had some EFI engines as well as some carburetors. The US started to abandon the use of carburetors in about 1988 so if you find a carb US spec Sentra B13 i can almost guarantee you that it didn't come with that engine originally.
After that you are on a hit and miss game.
You'll have to check out the links I posted to see all the mix and matches and even those leave out a few.