Tach reading high

Steve maybe there is a large drop in the charge path from the alternator to the battery. Clip the meter to battery positive, and the alternator stud. Run the car and turn on loads like lights, heater, whatever, and run engine on fast idle. This will give you an idea of the drop in that line. I don't know why the ripple reading is so ???

The ripple reading you mentioned is the NEW alternator?