Here's another update. After the spring got too stretched out of shape, the 3/4" bracket didn't do its job like it did 2 years ago. I had to remove the 3/4" bracket, then use a 1" bracket, and make a new hole slightly above the old hole. It's possible to start with a 1" bracket instead of a 3/4" bracket, but the extra tight spring tension will make it hard to close the door the first few times. It should work fine after this break in period.
Here's another thing which I came across. The 1989 van uses the same sliding door latch which the rear hatch uses on a lot of models (it has a small switch). The switch on the hatch version of this latch controls the automatic operation of the dome light. The sliding door has a pin switch on the body for the dome light so I assume that the latch switch might be used to indicate which door is open on the digital dashboard display.