Hi Trigg,
I dont think that the electric windows were standard on a 316 - they may have been installed by the dealer when the car was new, or anytime afterwards.
The seats don't sound too good

. Maybe you can get some second-hand ones from the wreckers. Otherwise everything else seems normal for an old car!
The single headlamps were standard on the 316 and 318. I never used to like them, but they have grown on me. All in all I like the little 316s and 318s - if you can find a good one they are an excellent fuel-efficient alternative to a boring little Civic or Corolla with better handling and chassis. The problem in Aust is that they are pretty rare; fuel was cheap in those days and so people just bought larger-engined cars if they were already forking out on a prestige marque.
Happy Driving!