4.6 75 shot Zex 764 Plug Gap?

Just went and bought autolite 764's for a friends 98 4.6 GT, which are equivalent to 1 step colder plug than stock. The car definately needs the colder plug for the 75 shot of Zex juice he has on it. Our problem is we're not sure what to gap the 764s at? stock gap? or a few ppl from around here are telling us to gap it at .058. I figured I'd hope to get some input from somebody who has the same setup, or just really knows what their talkin about. Any quick help would be greatly appreciated, plan on runnin it at the track tonight! thanks :thumbup