What is the largest laps led with the lotus-ford 34/3 chassis?
CREATE TABLE "indy_500_results" (
  "year" real,
  "car_number" real,
  "start" real,
  "qual_speed" text,
  "speed_rank" real,
  "finish" real,
  "laps_completed" real,
  "laps_led" real,
  "race_status" text,
  "chassis" text
);
SELECT MAX("laps_led") FROM "indy_500_results" WHERE "chassis"='Lotus-Ford 34/3';