The result was the IR (the initials standing for Iso Rivolta, although the company had no part in the car's gestation), designed by ex March engineer John Clarke.

[4] It featured double wishbone front suspension with upper and lower links at the rear, and outboard springs all round.

The new IR appeared at the fourth race of the season, the Spanish Grand Prix, with Ganley and the returning Galli at the wheel.

[10] Tom Belsø replaced Galli in Sweden but he only took part in practice (and was slowest) as it appeared no funding was available from his sponsors for the race.

[12] Henri Pescarolo returned to replace Belsø for the French Grand Prix, but retired with overheating problems while Ganley finished 14th.

[13] Graham McRae replaced Pescarolo for the British Grand Prix, qualifying on the back row, but he retired with a throttle problem on the first lap, while Ganley started 18th and finished ninth.

[14] Williams continued to rent out the second IR to paydrivers, and Gijs van Lennep replaced McRae for the Dutch Grand Prix.

In a race overshadowed by the death of Roger Williamson, van Lennep finished sixth, two laps down, with Ganley ninth.

[15] Pescarolo returned for the German Grand Prix, qualifying 12th and finishing tenth, but Ganley crashed heavily in practice due to brake problems, writing off the chassis.

[20] Wietzes failed to pick up the leader, staying in front of Ganley by mistake, which allowed several drivers including eventual winner Peter Revson to gain a lap on the field.

[21] In the subsequent confusion, some believed the leader to be Ganley, and others including Team Lotus manager Colin Chapman were sure it was Emerson Fittipaldi.

[6][22] After both had passed him, Ganley continued to battle with Stewart, Mike Hailwood, Revson and James Hunt until the end of the race.

[24] Jacky Ickx replaced Schenken for the season-ending United States Grand Prix and drove well to finish seventh with Ganley 12th.

[25] This was the final race for the car under the IR designation, and it had scored two points, leaving Williams tenth in the Constructors' Championship standings.

After backers Iso and Marlboro left before the 1974 season, the slightly revised car was renamed the Iso–Marlboro FW, and Frank Williams found that he was underfinanced.

[27] At the South African Grand Prix, Williams entered a second car (chassis "01") for Tom Belsø, who qualified last with Merzario an outstanding third on the grid.

The Dane retired on lap 1 with a slipping clutch but Merzario finished sixth, earning the team their first World Championship point of the season.

He raced well and was lying fourth when he went off the track on lap 38; his car went over the barriers, landing among a group of photographers, fortunately with no injuries.

[29] Gijs van Lennep returned for the Belgian Grand Prix, replacing Belsø, but the Dutchman qualified on the back row with Merzario seventh.

[31] Before the Swedish Grand Prix, Merzario had broken a finger in a sports car crash, and after a few practice laps, he decided against racing in Sweden.

[35] For the French Grand Prix, Jean-Pierre Jabouille was brought in to replace the Dutchman but he also failed to qualify (the last appearance for chassis "01"), while Merzario started 15th and finished ninth.

[48] At the Spanish Grand Prix, the young British driver Tony Brise replaced Laffite who was driving in Formula Two that day.

[57] Vonlanthen also drove the FW03 in the non-championship Swiss Grand Prix, starting on the back row and finishing unclassified, nine laps down.