yah i dunno i was really into the stanza before i got my car and i couldn't find much to upgrade, and trust me i really looked. as far as a rebuild kit yah they are easy to find, but like others said some of the parts in those kits are questionable. if you wanna have a side exit exhaust then a 240sx manifold might work lol cuz its gonna be pointing the wrong direction. and yah injectors are really unnecessary unless you are boosting or have a cam and some form of tuning, in which case you should probably already know that, or have lots of money and a competent/trustworthy engine builder/tuner who can take care of you. to be honest i found a shitload more aftermarket parts through this website than i found on ebay or any other american website.
89-92 stanza and pintara trx are practically the same car just dont get parts that wouldn't be compatible with rhd, i.e. steering rack, subframe, possibly brake or clutch cylinders, and the interiors are totally different (mostly huge parts that would be ridiculous to ship anyway). i think if i lived in aus and had a pintara i might get the us stanza guage cluster because i kindof like it, although the japanese cluster is nicer, but who knows if the plugs on the back are even the same, if they aren't you are really in for some fun wiring. if someone is looking for something in particular i might make a trip to pick-a-part soon (e-mail me), here hardly anyone owns/maintains stanzas so parts for them at the junkyard cost next-to-nothing (or nothing if they are "pocket parts")
there are probably more stanzas in the u-pull junkyards than on the road in the states sadly.