I dont totally agree with you, i believe that the most important element in fast bowling is pace... Line length and swing can be taught by a good coach, just like spin is the most important aspect of spin bowling pace is the most important of fast bowling.Bowling fast can only get you so far, there are bowlers who play club cricket here that have been measured with speedometers and can bowl speeds ranging from 130kph to 150kph, but they aren't near the international level yet.
To be effective against the best teams you need accuracy, coupled with swing and pace. Having pace means nothing if you can't bowl in the right areas so it's a fruitless endeavor to try and bowl as fast as you possibly can, but without taking wickets and conceding 4 wides when you bounce the ball over the keeper.
I recall reading about an English wicket keeper (can't remember who, but he's very well known) who could bowl 130kph+ at 15, but bowled full tosses at the rib cage all the time so he was useless as a bowler. Vernon Philander is a great example of using accuracy to take wickets as a seam bowler.
Shahidpak asked how they do it, one thing that I know adds quite a lot of pace is having a braced front leg. There are many articles and videos that discuss this, and it's something that spinners can use as well.
Mitchell Johnson gets most of his pace from his slingy action, by that I mean an action where the bowling arm comes through much later than in a normal action, allowing the muscles to wind up and release the energy in a more whiplike manner. Not neccesarily a low arm action but it usually is.