The Hillary Trail, named after Sir Ed Hillary, for whom this was a special place, is 75km in length and features 3,300m of vertical ascent. It is mostly technical single-track running/walking through some stunning bush and coastal scenery.
Note that an 80km race is held annually on the Hillary Trail. The race adds 5km to the route, and also skips one section of the actual Hillary Trail which is in a scientific reserve where events are not allowed:
"The 80km course follows the Hillary Trail from the Arataki Visitors Centre West of Titirangi all the way to Muriwai, via Huia, Whatipu, Karekare, Piha and Bethells. The event adds approximately 5km extra to the official Hillary Trail with a loop at the start, some extra distance at the end and a detour at Pararaha to avoid the beach section into Karekare as this is a scientific reserve as such no events are allowed on it."
FKTs listed here are for the 75km Hillary Trail itself. Race records can be found on the race website.