Had the same issue come up on the way back from Mexico this summer. The van sure get hot without AC.
I pulled the plug out of the fire wall in the passenger foot well. Then after some thought cut the vacuum line to the dash at the red line.
I used a cut up coat hanger to fish a string through the firewall. It came out just below and to the left of the fan.
Then taped the string to the new vacuum line and and pulled it through into the engine bay and up to the vacuum pump connector noted in OP.
The new vacuum ball does not have the in and out ports labeled so it took a bit of experimenting with a vacuum gauge and pump to figure out which was which. The one with the shield is the outlet.
The vacuum ball fits nicely behind the metal brace that holds the facial panel on the passenger side. Used Gorilla tape to hold it in place.
It is nice to AC again.