Agree with 427 Aggie here. I changed mine to a manual as well. That's option 1.
Option 2, assuming you want to stick with a power rack, you should be able to get these units with a slower ratio. You should just start contacting the manufacturers/distributors for info -- Flaming River, Heidt's, Fatman Fab, Stock Car Products, Summit, etc.
Option 3: figure out how to integrate a speed-controlled power assist unit (like the Hondas do) into a Mustang II power rack.
Option 4: slow down.
Cheers,
-Neil.