Make a suggestion- could be Sylvester Monaro. They did two, one for the circuit,other for Speedway. Try Grant at Sylvester Spares-he could help.
Don't recall a speedway car, thought it was one drag racer & one circuit racer, Neil Stuart might know, anyone have contact with him? IIRC it was a darker purple or even dark blue along with green & white colours on those SPCS Monaro's.