If they are in good shape dont chop them up. (Depending on the year anyways, do you have a 74-76 or a 77-78?) At least sell them and you could buy 2 or 3 sets of rusted out old ones to make the pipes you want. Besides you cant really just pull the baffles out like you can a 750. This is assuming you have the early style pipes.
If you have the late style, its a bit easier. The real work is that you are going to have to re-tune the carbs because of the change of exhaust flow. It will probably make your bike go slower or have an incorrect mixture at certain throttle ranges (without any engine mods).
Just sayin'