I've tried that, as I said I keep hitting the water outlet with the bracket.

Without seeing it in person or good pics, it's hard to help. Best I can suggest is compare the old alt and the new and determine why the new alt is interfering and use your best judgement to come up with a solution.

Is there a bushing (on one of the mount bolt holes) that gets pushed in that needs to be pushed back out (with a bolt+ washers + nut)? On a VW with Bosch alt I need to do that but I do not remember if that's the same in a W123.

__________________
85 300D turbo pristine w 157k when purchased 167,870 July 2025
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked