If you are mostly torso, then look at the Tarmac's geometry and see if it has enough room for you. In other words, not all bikes are created equal and on some it's very difficult (given a particular rider's body dimensions) to tweak it to fit.
I fit bikes and it's very seldom that we need to change cranks if the frame fits. Frame has to fit before anything else or you are cramming a round peg in a square hole.