Well, this may seem elementary but I wonder if you can see the leak source from below while engine is running (assuming all safety precautions taken) with a flashliht locate the weep holes (visible at top + bottom).
The H20 pump change on my 79 300d
did not require radiator and shroud removal.
(no york type A/C unit).
Your set up may be more complicated.
I did see my leak from bottom weep hole
while in supine position