>Completely? Does this mean that the later door's rear (center) rollers
>won't fit the earlier rail, or that the later rail won't fit the
>earlier body? This is the one thing that would stop me fitting a later
>door to my earlier van.

not sure about the center rollers, they should be the same, I've never tried fitting older door on newer van.

>
>> 84 and older have a crappy rear latching system and the outside handles tend to break off.
>
>My 84's door hasn't had any problems with the latch (though it's a
>total pain not being able to flick the lock knob and slide the door
>shut to lock it). Not that I used the van for long before the trans
>gave up and it was off the road.
>

The main difference is the rear latch in center of the door (on the C pillar?)  84's and earlier have a crappy little stub perpendicular to the body, 85's and newer have a meaty stub at a 45 degree angle which make it much easier to open and close the door.

85's and up also allow you to lock the door before closing it, a nice convenience.

I think the windows are slightly different sizes too between old and new style sliding doors.