An early 900 will be carbed, ie is injection and Sie is injection with some extra bits inc the floating rear caliper you refer to. There are other differences between the models and even between the same models depending on year. (inc rear hoop suspension or not)
Just to throw something in to muddy the waters further I like the look of this one. Injected though (I know you said you wanted early so you can do your own work) but the 1000 is widely considered to be an outstanding engine.
http://www.ebay.co.uk/itm/301600515095