The 14" E30 rims are likely what are usually called "bottlecap" rims, sometimes "turbine" style. I forget the BMW Style number.
The "vane" style that came with the 320i cars have 20 spokes (if I understand what you're saying) and look like the Alpina rims everyone's hot for. The were and inch larger in diameter than 2002 stock 13s, and were often retrofitted to 2002s. They fit nicely in the back, but in front would rub when going over driveway curbs. The rubbing was on the inside rear of the wheel well. You learned to take driveways head on, rather than at an angle.
In your situation (note: I have no direct experience with the 2000 C or CS cars) it sounds like the offset is just wrong enough to be a problem up front. As you noted, some limited grinding may accomplish a fit, but I'd be careful about grinding a caliper unless I was sure of exactly much I needed to grind, and maybe had a spare caliper on hand. Longer studs and thicker spacers might be a better option.
Look and see if the rubbing is the same on both sides, not that you can do much about it but I have heard (and this is after all the Internet...) that some car bodies were not centered on their suspensions.
