I can highly recommend Magnecor leads I have run both their 8mm & 10mm with great success, not only with improved spark but lower RF interference as well.
Check out their site
http://www.magnecor.com.au/, thunder cords is the Australian distributer for magnecor leads, they can customise leads to your requirements. They have alot of great info on their site, and have great experience in the performance car industry.
If you call them speak with Neil & say hi for me
cheers
Scott