https://en.wikipedia.org/wiki/Porsche_911
The C series was introduced in August 1969 with an enlarged 2.2-litre engine (84 mm bore x 66 mm stroke). The wheelbase for all 911 and 912 models was increased from 2,211–2,268 mm (87.0–89.3 in), to help as a remedy to the car's nervous handling at the limit. The overall length of the car did not change, but the rear wheels were relocated further back. Fuel injection arrived for the 911S (901/10 engine) and for a new middle model, 911E (901/09 engine).
I'm not aware of a SWB kit (plastic or resin) ever being offered. The 911S kit has the narrow body style.