[sybir]

Don't run spacers on stock studs period - it's a bad idea on a street car, bad idea on a GC/GM with early bearings, etc, let alone on a car that sees the abuse a rally car does. 3mm MIGHT give you almost enough engagement, but it's totally dependent on seat thickness, etc.

Also, if the offset doesn't change, you get an even split between front and back faces - offset is the hub mounting flange relative to dead center on the wheel, not either edge. If you go to an inch wider wheel, you add a half-inch to the inside, 2 inch wider wheel, an inch to the inside. The offset may change significantly between your steelies and your alloys, which is why the wheel moves around relative to the hub mounting flange. - by definition, a change in the front-rear (or inside/outside, if that's easier to visualize) balance of a wheel means the offset is different.

You might be able to run a wider wheel, or a lower offset wheel, like a 16x7.5 or 16x8, but with a fixed tire width like a 205, the increased wheel width will just stiffen your sidewall, which may or may not be an optimal change. Keep in mind a significantly wider wheel, and more importantly a lower offset wheel (moving the leverage point farther out) will have increased bearing wear especially in off-road conditions due to increased load, and you mess up your steering geometry - that may be a huge deal, or may not be something that bugs you, but it does change how the car turns in and returns to center, and again puts more load on all of the front end components.