make sure you get the right transmission
there are 2 different types of b-series transmissions
theres a "cable" transmission which uses a clutch cable instead of hydraulics
then theres a hydraulic transmission which uses hydraulics that we all know and love...
within these there are 3 different gearset combinations, which can be very difficult to figureout or pick, both styles you can get LSD's but only the cable transmission has a mechancial speedometer port, which may or may not bolt to the hydraulic transmission
then you have to decide how new you wanna go, theres OBD-0, 1, and 2 with teh b16a, obd1 is the easiest to modify the computer, obd2, has a bunch of wires for emissions and whatnot.. if you dont care about polluting the world, get obd1, and dont deal with the catalyst, but the engine is pretty much the same regardless of which year you get, aside from the distributor plug harness, everything will mix and match, and are pretty much identical with the exception of the OBD-0 exhaust manifold as it has 2 oxygen sensors, whereas the obd1, and 2 have a single oxygen sensor on the manifold, wiring for the any of the engines should be pretty simple, however the newer engines have more gadgetry and less vacuum ports
hope that helped