Any 185 in Australia from 1979 model carries the ER model suffix. They all pretty much look the same as the 79 models, with only very few few minor updates since then. You can at least consider 99% of the parts from any model on from 79 will fit your model what ever it ends up being, but like i said things change in 92 with the electrics. Any parts that have different part numbers are generally updates and improvements suzuki made and will fit the older bikes
The basic motor from the 79 on ER models is the same as 77-78 (77 was the first year for the center port case reed model) however the first couple models had slight differences in heads, barrels/porting, carburettor size etc. The 77-78 had 32mm non leading axle forks and the 79 on ER series had 33mm leading axle forks. 77-78 had a round steel swingarm and 79 onwards had square steel swingarm. Some markets did not get the new ER spec bikes in 79. For example USA did not, They had updated 78 models and got 32mm leading axle forks. Hubs are the same for all models but 77 had alloy rims. If you are looking on USA parts sites such as
www.alpha-sports.com, you should only be looking at 80-81 for parts, but keep in mind there are some differences with the USA models too. In USA they did not have the ER model designation. For 80 they were just a 185 T and 81 185 X. They did not get the 185 after 82. The USA model does not have a tacho either. They have this blanked off on the engine and instead of the tacho the idiot lights are situated in its place rather than the center console on the bar mounts.
Also many USA parts sites will list a lot of parts as NLA, but they are infact available. i suggest you stick to using your local dealer, another Australian dealer or maybe
www.cmsnl.com The 185 is still sold in markets outside Australia so you can still get almost any part brand new for these.