There is at least one good head and shoulder photo of John McMillan on this forum - maybe try search Ray - but to be fair I do not think his photo had a title.
There has been some traffic on facebook recently about Mrs McMillan and her crash in Wellington [ Talbot Lago??? & truck ]
The Jackson Special was designed to be the prototype for a run of chassis which a buyer could turn into a race car. Sponsored by Jackson Engineering, designed (and built?) by John. Tube chassis with an almost identical set of tubes a few inches above the base chassis, I could measure but not more than 4" separation. What more do you want to know Ray?