Somewhere, and I will probably find as soon as I post this reply, there is a newspaper clipping of an aerial photo of the three circuits used at Renwick. I couldn't find it so I sketched this layout on a tracing from an online map.
Circuit No 1 was used only in 1960 and was about 1.08 miles long, at the western end of Renwick township.
Circuit No 2 was used only in 1961, about 1.25 miles to the lap (a 50 lap race)
Circuit No 3 was used for the remaining 5 races, 1962 to 1966, and was 1.5 miles to the lap.
I believe there was a chicane in Havelock St(which was part of both circuits 2 and 3) and the State Highway 6/63 intersection may have been different over the years.
Probably someone who actually went there can tell me how much of this is wrong!
Stu
OOPS : Long way to Nelson via State Hwy 63! Better via Havelock on S.H. 6.