The 99-01 Cobra IRS is 28 spline inner and outer, The 2003-2004 IRS is 31 spline inner and 28 spline outer.
Hub to hub, the Cobra IRS is about 1.8" less wide.
The knuckles are not comparable, however they use the same hub bearing, so the hubs will swap.
On the Cobra IRS, camber is adjusted via an eccentric in the upper kunckle bolt, toe is adjusted via a tie rod.
Here's a couple of pics.