I have put a Weber 32/32 progressive carb on an M103. To see my vehicle search "Mercedes W124 with custom distributor and Weber carburetor - M103 engine". I built a custom distributor and used none of the stock ignition. It was a lot of work.

If you have questions please let me know and I'll be happy to help.

YouTube video is here: https://youtu.be/8Ht7-KZCNGk