[Perfectlap]

1999-2001 996 Carrera and Boxster are essentially the same car from the doors to the front bumper. It's 99% from the 996 parts bin.
Installing the 996.1 GT3 front bumper on the 986 is a piece of cake.
Also, I think the proportions are perfect. The 996.2 GT3 front bumper is a bit wider and longer and only available from the aftermarket for the 986 so installation is not as simple. and you'll probably need at least 18" wheels to fill the bigger wheel well space created by a bigger front bumper. Both 996.1 and 996.2 GT3 bumper are larger than the stock 986 S bumper so I think skirting is necessary to even out the the shape. Otherwise it looks like a skinny arrow from the side.