Is there a generic bulb set that would suffice to have spares for a 320 gt?

I can't be sure but I suspect that they are just standard auto bulbs. Readily available locally at service stations, bigger supermarkets etc.

You could always take the covers off and check each bulb bur I would beware of mission creep. A little bit of fine fettling can often lead to a major disaster with a broken plastic cover or the like.

I had a side light bulb blow recently (the white/red lamp at the top of the front of the body). The bulb that had blown was unreadable, so i popped into Halfords and saw at least 7 different options of size and wattage for festoon bulbs (plus LED options too). Size/length was easy to determine, but wattage not so much... I went onto the Forum on my phone and found a post from Randa saying 5W, so that's the ones i bought and it proved to be correct!

So you will need C5W 239 5W for those lights.

Replaced all mine with LED equivalents. Only thing is to be careful with the indicators, you need to check the angle of the bayonet pins and get the type with built in ballast resistors. The replacements look great, nice and bright.