How to Determine the Best Message Type to Use in Service Operation

We need to create an outbound synchronous service operation to a third-party (Non-REST Web Service).   The third-party needs our Message Structure to be in the following format.  What type of Message Structure should we use?   We can't use RowSet-based because it will insert PSCAMA.

<DownLoadEquipment xmlns="http://tempuri.org/">

      <msgData>

        <clsVehicleData>

          <UnitNo>string</UnitNo>

          <BillingCode>string</BillingCode>

          <BillingDesc>string</BillingDesc>

          <EquipClass>string</EquipClass>

          <DeptNo>string</DeptNo>

          <UnitID>string</UnitID>

        </clsVehicleData>

        <clsVehicleData>

          <UnitNo>string</UnitNo>

          <BillingCode>string</BillingCode>

          <BillingDesc>string</BillingDesc>

          <EquipClass>string</EquipClass>

          <DeptNo>string</DeptNo>

          <UnitID>string</UnitID>

        </clsVehicleData>

      </msgData>

    </DownLoadEquipment>

  </soap:Body>