Did T4 become T5?
This is Martin Tanner's T4 at Waterford Hills in 1961. There is evidence from T5's prior owner that T4 morphed into T5 for 1962, which just adds to the legacy of T5.
I also have an article enroute regarding T3, and how T2 was panned by many as being substandard to Tanner's skill level, much to Tanner's disgust. T2 still won races years after by second owner Frank Isaacson, so you can knock it all you want, it still took home hardware.