The license plate 2PCE154 shows up twice. It's first on a van parked in Clark's father's driveway when the book club ladies are there, and then on Kellen's brown truck when they do the ransom drop.
It later shows up on S1E14, again on two different vehicles.
Clark's FBI SUV has the license plate 2CQN654. This plate was also used in The Rookie S5E3 on a pickup truck and in S.W.A.T. S6E2 on a van rented by kidnappers.
The license plate on the FBI surveillance van, 3JRQ158, was also used on The Rookie S5E7 on a murdered doctor's car.
The license plate 2WAC233 shows up here on the kidnapper's red Jeep, and also in S1E14, on a parked car when the Feds pull up to where Finn has just shot Langham.
When the agents witness the kidnapping, Stenson calls in and reports the van's license plate as KI9809. It was actually 3IDW674.