Hello Pierre,
My mechanic installed a 1987 and newer type alternator in my 1979 Porsche 928. It required machining a custom part and use of brackets and pulleys from a newer car. See the attached PDF documents.
Rich
Membership Chairman
Charter Member
1993 928 GTS Cover Girl
1987 928 S4
1979 928 5-speed rescue
1979 928 5-liter track beast