Hi mate,
In a car weighing 800 odd kgs HT10 are 880 degree maximum would be probably be massive overkill. If it's a dedicated race car I'd look at the QFM Comp 9, and for your Willwood calipers are $229 per axle set.
The Comp9 are 0-800 degrees, with similar friction levels to a Ferodo DS2500.
Allow 5-6 weeks for manufacture also, as this isn't a pad we've got in stock. Once you've ordered it once we'll continue to keep a set on the shelf for next time though.
Regards,
Greg