You will still need the Add-On INSTALLED

Find vehicles.meta in mods/update.rpf/common/data/levels/gta5, then find the police3 lines and replace them with these:

    <Item>
      <modelName>police3</modelName>
      <txdName>police3</txdName>
      <handlingId>SDELUXE47</handlingId>
      <gameName>police3</gameName>
      <vehicleMakeName></vehicleMakeName>
      <expressionDictName>null</expressionDictName>
      <expressionName>null</expressionName>
      <animConvRoofDictName>null</animConvRoofDictName>
      <animConvRoofName>null</animConvRoofName>
      <animConvRoofWindowsAffected />
      <ptfxAssetName>null</ptfxAssetName>
      <audioNameHash>flatheadv8p</audioNameHash>
      <layout>LAYOUT_STANDARD</layout>
      <coverBoundOffsets>EMPEROR_COVER_OFFSET_INFO</coverBoundOffsets>
      <explosionInfo>EXPLOSION_INFO_DEFAULT</explosionInfo>
      <scenarioLayout />
      <cameraName>DEFAULT_FOLLOW_VEHICLE_CAMERA</cameraName>
      <aimCameraName>DEFAULT_THIRD_PERSON_VEHICLE_AIM_CAMERA</aimCameraName>
      <bonnetCameraName>VEHICLE_BONNET_CAMERA_STANDARD_LONG</bonnetCameraName>
      <povCameraName>DEFAULT_POV_CAMERA_LOOKAROUND_MID</povCameraName>
      <FirstPersonDriveByIKOffset x="0.000000" y="-0.055000" z="0.000000" />
      <FirstPersonDriveByUnarmedIKOffset x="0.000000" y="-0.025000" z="0.000000" />
      <FirstPersonProjectileDriveByIKOffset x="0.000000" y="-0.120000" z="0.030000" />
      <FirstPersonProjectileDriveByPassengerIKOffset x="0.000000" y="0.030000" z="-0.040000" />
      <FirstPersonProjectileDriveByRearLeftIKOffset x="0.000000" y="0.000000" z="0.000000" />
      <FirstPersonProjectileDriveByRearRightIKOffset x="0.000000" y="0.000000" z="0.000000" />
      <FirstPersonDriveByLeftPassengerIKOffset x="0.000000" y="0.000000" z="0.000000" />
      <FirstPersonDriveByRightPassengerIKOffset x="0.000000" y="-0.055000" z="0.020000" />
      <FirstPersonDriveByRightRearPassengerIKOffset x="0.000000" y="0.000000" z="0.000000" />
      <FirstPersonDriveByLeftPassengerUnarmedIKOffset x="0.000000" y="0.000000" z="0.000000" />
      <FirstPersonDriveByRightPassengerUnarmedIKOffset x="0.000000" y="-0.035000" z="0.000000" />
      <FirstPersonMobilePhoneOffset x="0.133000" y="0.228000" z="0.468000" />
      <FirstPersonPassengerMobilePhoneOffset x="0.136000" y="0.223000" z="0.425000" />
      <PovCameraOffset x="0.000000" y="-0.240000" z="0.590000" />
      <PovCameraVerticalAdjustmentForRollCage value="0.000000" />
      <PovPassengerCameraOffset x="0.000000" y="0.000000" z="0.070000" />
      <PovRearPassengerCameraOffset x="0.000000" y="0.000000" z="0.070000" />
      <vfxInfoName>VFXVEHICLEINFO_CAR_GENERIC</vfxInfoName>
      <shouldUseCinematicViewMode value="true" />
      <shouldCameraTransitionOnClimbUpDown value="false" />
      <shouldCameraIgnoreExiting value="false" />
      <AllowPretendOccupants value="true" />
      <AllowJoyriding value="true" />
      <AllowSundayDriving value="true" />
      <AllowBodyColorMapping value="true" />
      <wheelScale value="0.209400" />
      <wheelScaleRear value="0.209400" />
      <dirtLevelMin value="0.000000" />
      <dirtLevelMax value="0.700000" />
      <envEffScaleMin value="0.000000" />
      <envEffScaleMax value="1.000000" />
      <envEffScaleMin2 value="0.000000" />
      <envEffScaleMax2 value="1.000000" />
      <damageMapScale value="0.600000" />
      <damageOffsetScale value="1.000000" />
      <diffuseTint value="0x00FFFFFF" />
      <steerWheelMult value="1.000000" />
      <HDTextureDist value="5.000000" />
      <lodDistances content="float_array">
        12.000000
        30.000000
        60.000000
        120.000000
        500.000000
        500.000000
      </lodDistances>
      <minSeatHeight value="0.85" />
      <identicalModelSpawnDistance value="100" />
      <maxNumOfSameColor value="10" />
      <defaultBodyHealth value="1000.000000" />
      <pretendOccupantsScale value="1.000000" />
      <visibleSpawnDistScale value="1.000000" />
      <trackerPathWidth value="2.000000" />
      <weaponForceMult value="1.000000" />
      <frequency value="40" />
      <swankness>SWANKNESS_2</swankness>
      <maxNum value="10" />
      <flags>FLAG_LAW_ENFORCEMENT FLAG_EMERGENCY_SERVICE FLAG_NO_RESPRAY FLAG_DONT_SPAWN_IN_CARGEN FLAG_REPORT_CRIME_IF_STANDING_ON</flags>
      <type>VEHICLE_TYPE_CAR</type>
      <plateType>VPT_BACK_PLATES</plateType>
      <dashboardType>VDT_ZTYPE</dashboardType>
      <vehicleClass>VC_EMERGENCY</vehicleClass>
      <wheelType>VWT_LOWRIDER</wheelType>
      <trailers />
      <additionalTrailers />
      <drivers />
      <extraIncludes />
      <doorsWithCollisionWhenClosed />
      <driveableDoors />
      <bumpersNeedToCollideWithMap value="true" />
      <needsRopeTexture value="false" />
      <requiredExtras />
      <rewards />
      <cinematicPartCamera>
        <Item>WHEEL_FRONT_RIGHT_CAMERA</Item>
        <Item>WHEEL_FRONT_LEFT_CAMERA</Item>
        <Item>WHEEL_REAR_RIGHT_CAMERA</Item>
        <Item>WHEEL_REAR_LEFT_CAMERA</Item>
      </cinematicPartCamera>
      <NmBraceOverrideSet />
      <buoyancySphereOffset x="0.000000" y="0.000000" z="0.000000" />
      <buoyancySphereSizeScale value="1.000000" />
      <pOverrideRagdollThreshold type="NULL" />
      <firstPersonDrivebyData>
        <Item>STD_DOMINATOR_FRONT_LEFT</Item>
        <Item>STD_DOMINATOR_FRONT_RIGHT</Item>
      </firstPersonDrivebyData>
    </Item>
