Originally Posted by
justinzane
Imagine for a moment someone with a car hobby... They have an old car that they love and have painted, chomed, etc. They decide to replace the 4 cylinder engine with a rebuilt 6. They do not have to change the transmission to accomplish this. They could instead decide to replace the 5 speed manual with a 6 speed.
Have you actually done an engine or transmission swap on an old car? It's vastly more complicated and costly than you suggest and certainly not something done "on the fly". Changing the indexing disc in a brifter or changing an entire brifter is trivial by comparison.