Far more Vanners on here more knowledgeable than me, lol...
Just did mine on the '88 B250. if the linkage fell apart, it will be flopping around under the cowl. A few other things might be going on, such as: If the motor is inop:
Check to see if a fuse is blown. Fusebox is in the glovebox. Pay attention to those antique glass fuses for corrosion. I have never seen a wiper motor fail, but:. Make sure you have 12 volts at the motor when the switch is on. You should have continuity through the wiper switch when on. If you have power when on at the motor, that shows the switch is good.
If the failure is mechanical, in the wiper linkage under the cowl, you can easily fix it. No worries. A plastic bushing in the linkage will break, then the linkage rods will fall out. These can be replaced. Raise the hood, remove the wiper arms, kinda tricky, examine the arm, it only comes off one way. Unscrew and remove the cowl. Remove and replace ALL the wiper bushings, if broken. Reassemble, setting the wipers in the off position.
A Factory service manual for these Old Girls really helps. Good Wrenching!!