Don is a good example of the Indian summer for 500cc racing that occurred in the United States in the late 1950's and into the '60s, albeit as one make series, in all but name, for Coopers.
Don started in the later part of 1960 and took third in the SCCA national championship in his first full year, 1961 behind John Gadwa and Dick Hagy. He took a step back to fourth in 1962 as John Field came to the fore but beat John to the 1963 title.
Some results for Don:
Virginia International Speedway, April 1963
Please get in touch if you know more of Don's life.