Wiper motors on 67-68 barracudas

In my experience, that variable 3 speed switch is more problematic than the motor. If the motor runs and its park switch works, you might just clean it up, make it look new. Maybe flush the gear box and add new grease. New rubber mounting grommets are available if needed. The 67 linkage has bronze bushings at points which maybe worn egg shaped and noisy. The 68 should have replaceable black plastic bushings.