You may want to check the caliper groove size, from memory it's 22mm and the magna discs are 23mm so I had to machine the caliper groove wider. You can also machine a spacer up to fit in-between the two halves.
These were my costs, Magna rotors new are $65, $30 for seal kit, $35 for braided lines, 2nd hand calipers $120. Most expensive was the project mu pads but they are fantastic!
Your right about pads, the only options are 4wd ones and they aren't the best. I used rx7 pads as per the s13 caliper but you have to drill new pin retainer holes(no hard). You get a bigger pad area with these too.
Tir33d, Try GSL rally sport in qld, they are really helpful and he told me about the pad mod. They make pads as well and will do one to suit your application. They have a similar compound to the project mu's that's suitable for street/track, I've tried this but wasn't up to track days for me. Think they were round $140 Inc post.