Yeah, I know it's an old car but when I got my first E30, an 1988 325is, I was blown away that parts and advice were easier to get for that car than for my '98 Nissan DD.
Parts I (was) looking for are (were)
Hose from Upper rad to Thermostat: 11531708826 This number appears on the actual hose, which is convenient! The dealer said that there are four of these hoses at the factory. (4!, gettem while they're hot!))
As long as the hose above needs replacing, I’ll replace also:
Lower Rad to Thermostat: 11531278925
Thermostat to Water Pump 11531265448 This hose changes mysteriously in the era 1985-1986.
And I'll order thermostat housing parts which show common part numbers on RealOEM, so no issue there. One issue I do have with Real OEM, or perhaps BMW, is that the parts diagram doesn't match reality; it's a bit non-predictably schematic.
The build date of the car comes up on RealOEM as 1/86 but it seems like the break between 'old 1985' and 'new 1986' was more of an evolution than a sudden break.
I sent Bavauto a plea and they will bring in the one hose from Germany and ship the rest complete.
Even though their drop down model menu doesn't include my car I've dealt with them in the past and been quite happy.
I think that http://www.autoteile-meile.de/
site is going to be darned handy in future.
I have drum brakes in the back...