fuchs, 944 arms, bigger brakes possible

[Moctesuma]

Hello,

I'm building a 63' 1200 and I'm facing a dilemna-> I have in my garage a pair of late 944 alu arms, which widten form ~70mm the track on each side.
I also own two 944 steel arms, with their calipers.

I want to mount custom 15x10 fuchs wheels (widened) with a really small ET (somthing like ~5).
If I use the late alu ones, my car will need at least +10cm inner and outer widened Kerscher fenders. And I'm not even sure that it will be enough.
So here is my question: Wich arms would you use, if we assume that I WANT to use the fuchs, and be able, later, to mount bigger brakes (993 disks and callipers)(is it possible with 15'' Fuchs?).
I measured the rear track with the late alu and Fuchs and it's 1800mm wide, really much.

Thank you for your precious help