Another 911 race car history qn: when did the RSR's etc move from 3.0 to 3.2

[obrut]

Trying to determine when the 3.0RS, IROC and 3.0RSR type cars (either factory or privateer builds) started moving to 3.2 capacity or higher.

For example, cars running in IMSA or SCCA events.

[JeremyD]

They really went 3.0RS to IROC then started racing the Turbo's (1975) then went 930/934/935

Didn't get into the 3.2's until the 962 engines (that they Turbo'd)

[obrut]

Thanks Jeremy,

A lot of these 3.0 litre na cars kept racing for many years (decades) and kept being developed. I'm trying to work when such cars may have gone to 3.2 or 3.5 for imsa and various other sports car series.