The engine ran "a little" rough. I thought I'd found the culprit when I took out the spark plugs and one of them seemed to have no metal "hook" thingy. Unfortunately, this turned out to be just an other make and kind of spark plug. I have put in new spark plugs to be on the safe side.
The gaskets on the carbs were in a sorry state as well. When the car hadn't been started in a couple of days petrol gushed out of the carburetter until the gaskets had been wetted again. I've ordered a couple of SU gasket sets. It turned out to be a bit of a detective job as there is no description provided which gasket goes where, and it seemed some things (like the rubber o-ring on the idle adjust screw) had just disappeared with the years. Luckily, there are detailed photographs on the SU website if you click on the right kind of type.
One of the float chambers had some petrol inside. Although I couldn't find the leak I thought it would be a shame to throw it away (a new one is about €30 I believe) so I've drilled a 3mm hole in it, shaken out all the fuel inside and left the remains to evaporate, and then I've soldered it shut with my regular electronics soldering iron. It seems ok now, and if it's not, it was worth the try.
After placing the carb setup back - an annoying job, there's no room for a ratchet so you have to put 8 nuts on at 1/4 of a turn at a time) - I noticed one of them is still leaking some fuel, so the diaphragms and springs will be replaced as well.
For now, the engine is running, I've set up the carbs "more or less" right but the engine isn't running smooth or quiet.
I've changed the fan belt and alternator belt as well.
As for the power steering, the pump had no oil in it whatsoever. I've refilled it and it seems to be holding its oil pretty well. I've ordered the gasket set nevertheless, but I won't be rebuilding this pump until I'm sure it needs doing.