I'm a little confused, too. If you really want a twin-disk, most of the things I've read about Mcleod have been excellent. Monster apparently also makes a good twin. If that's the ballpark, why not just go with them?
I will, one day, get another stock-blocked turbo fox and run about 500rwhp on the street. When that happens, I will not be interested in running a $1000 twin-disc clutch. I would rather push the limits with $400 clutches.
In fact, actually, I know exactly what I'm going to do. My best friend had a great experience with these guys:
MUSTANG/CAMARO Performance Manual Transmissions/Clutches/Repairs/Parts/Gears FL
I'm currently working with Wally on the g-force geared T56 that they're building for me, and I can tell you that their philosophy is that choosing the right clutch saves your transmission. I didn't expect to want to use them, but after about a 30 minute discussion with him, I felt like he really really knew his
. On the page I linked, it looks like they've got single disc clutches that they recommend all the way up to 680hp, none of which cost more than $420. They even have a "last stage" 700-800 hp single disc clutch, but they say that it's very hard on transmissions.