[racer]

From 69-73 Porsche offered a "T", an "E" and an "S". For 1974 they offered the base (911) the "s" (911S) and Carerra.

The 911 had a 2.7 with approx 150hp
The 911S had a revised 2.7 with 167-175hp depending on rating (Sae or Din)
the Carerra used the same motor as the "S" for the US market.

IIRC, the main difference between 911 and 911S was detuned motor, trim packages too. It is possible that the 911 also had smaller brakes and smaller torsion and sway bars than the S, but I really can't remember.

The carerra added to the S with the Ducktail, optional chin spoiler, rear flares, more trim differences and I think I read somewhere, some aluminum rear suspension components.

The 74's also had a more desireable final drive ratio than later 2.7 cars. They were also the litest of the midyears (smaller rear bumpers, standard manual windows, sunroof was optional etc. by '77 most cars were ordered heavily optioned by dealers)