What is the best type/brand of leads for a performance 6?

most definately eagle f1 spiral cores, or queensland ignition lead (spiral core also)

since your in sydney, head up to Joe's @ liverpool as hes the nsw rep for the Queensland Ignition Leads, you can get both brands in a variety of colours and vary size from 8mm to 10.5mm wide (best to get just 9mm) and about $75-95 a set.

Cheers mate. Do you know their address or business name?

Crescent Motorsport - 54 Macquarie Street, Liverpool 2170.

sales@crescentmotorsport.com.au