You could already visit the Mario Wiki to see what each individual kart accessory did to your overall stats in Mario Kart 7, but YouTuber nxtnico does you one better. The video embedded after the jump shows you a stat chart for every conceivable combination of body, wheels and paraglider the game has to offer. It doesn’t look like the stats of each individual racer are taken into account here, but it’s a pretty nifty tool nonetheless.
The list itself is in German, but nxtnico says an English translation is on its way. Watch the comments embedded in the video and it isn’t too tough to follow along. I don’t know about you, but in building my own custom karts, I try to maximize speed, the other stats be damned. This is a pretty good reference for that.