I use my '78 SC strictly as a weekend toy as it replaces the Ducati my wife won't let me ride anymore. In that situation and the motor I built the 46 Webers I have are irreplaceable. I have a 3.0 motor with 10.5:1 pistons, GE60 cams, twin plug, headers and a car that's stripped of most anything that isn't welded on; 400 plus pound reduction. It's as fun to drive as any motorcycle I've ever owned and I've had a bunch.
It really boils down to what you plan to do with your car. If it's a daily fix the CIS but if you want to have some real fun look at carbs, cams and pistons; you'll never regret it.
Lindy