Actually, there have been three different alternator HARNESSES for the vans: 1984, 1985, and 1986-89. All are now NLA. The differences in the harnesses have nothing to do with the connector to the alternator itself, but rather other connectors included in the harness. 1984 has no oil level sensor wire because there's no oil level sensor. 1985 has oil level sensor wiring connectors that only mate with the 1985 (3Y) oil level sensor AND the corresponding oil level sensor wire in the 1985 chassis wiring harness. The function of the wire is identical to the 1986-1989 oil level sensor wire, but the connectors won't allow the harnesses to interchange without splicing in the appropriate connectors (guess how I learned ).

The alternators themselves are totally interchangeable and the same for all years despite part number supersessions.

I'd get a Denso (or rebuilt Denso) alternator. Even if for some bizarre reason the harness on your van has been molested and has a nonstandard connector, a spare alternator is always a good thing to have on hand.

Gwen