Re: 883-1200 conversion...
Rerrion,
To make your Sporty a real sleeper, do the 1200 cylinders and pistons with Buell Thunderstorm heads, hotter cams. Thunderslide and rejet the carb, free up the intake and exhaust. Once done you won't believe it's the same bike.
As far as vibration is concerned, it will probably be smoother than before since the breathed on internals will have had the mechanics touch, as in hand built. My 95" FXDX with the works is noticeably smoother than stock. Really hits hard at idle but from there on up, the faster you go , the smoother it gets.
You see; high performance parts tend to be of higher quality, better balance, closer tolerance than thier oem counterparts.
Later,
Mike