I haven't followed the Singer story closely so feel free to correct. I believe they use all new engines in their cars built by Cosworth but based on a modified (by Cosworth engineers?) 964 design. The "Williams engine" is a further redesign (I assume done in collaboration with Cosworth) of the same Cosworth redesign of the original 964 design, which is then built by Cosworth.
First 2018 Livery is up, and it may be time for a new thread. https://www.f1fanatic.co.uk/2017/12/02/sauber-unveils-concept-alfa-romeo-livery-2018/
Like this one? https://www.motoringalliance.com/forums/off-topic-racing/29679-f1-2018-a.html And you're right, time to migrate over there.