You will need to contact Moen directly at 1-800-289-6636. Their technical support will be able to help you.
Widespread means that the T6620 can be used from 8" to 16" on centers. The T6620 is only the trim so you would need to order a 69000 rough-in valve to complete the faucet.
All Moen Faucets with the SKU number beginninig with a "T" will require a faucet valve. This will be the same for any Lavatory faucet or Shower Faucet beginning with "T"