The correct 20T driven speedo gear is: C8SZ-17271-B / Orange / Available from Ford / MSRP: $3.75 // FTE sponsor PARTSGUYED.COM price: $2.70.
IMO, a 20T gear is one tooth too many for a speedo that is reading 20 MPH fast.
C7VY-17271-A .. 19T Driven Speedo Gear / Tan / Available from Ford / MSRP: $2.98 // PARTSGUYED.COM price: $2.15.