Here is a quote for the harness you need to use with your Mando alternator.
84-861236A2 HARNESS (MANDO ALT. USED) $325.00
I did find one person in Canada that has one of these harnesses in stock so I could supply
So just to review:
1) Mercruiser no longer supplies the harness that is used on your engine with the Mando Alternator, but
I did find a guy who has one of these harnesses in stock.
2) You could swap you alternator over to the Delco alternator but you would need to change the mounts
and the belt to do so (we can provide).
3) Or you could purchase the Delco harness and rewire to fit your Mando. This is a little complicated
as you would have to re-pin and do some splicing.