On January 20, 2013, it took him 18 days to cycle 81km one way from Mangatainoka to the signpost at Bluff with Steve. He took rest days along the way at main centres.
"It was on my bucket list the last time but this time I had to do it again before I get too old," he says, revealing Steve, who is a Ramblers Cycling Club member, "is keen as mustard". "Janet, my lady friend, thinks I'm crazy and she's probably right," he says with a laugh from her Havelock North home.
His other family members will cycle with him to keep him company during different legs of his journey.
"I'll be riding a 24-speed bike but when I was 16 years old I just had a one-speed one with no such thing as gears in those days."
On March 31, they will gather at a relative's home in Invercargill for a big celebration to reminisce "in a sort of family reunion".
He will sleep in a motor home while drivers will change along the way.
"Nobody is silly enough at 90 to do this," McGavock says with a grin.
"I used to jog years ago but stopped because my knee packed up so I started cycling again."
The bloke, who ran a Rotorua Marathon in the 1970s, takes a moment to ponder why he gravitated towards protracted rides but draws a blank with a shrug of his shoulders.
"You do it for recreation but also when you get older you've got to have something else to look forward to."
His first flirtation with cycling began with milk runs in Hastings but never extended to a competitive environment.
Interestingly enough, he didn't find himself in a cycle saddle from the time he was in his late teens until 2007 when the Central Otago Rail Trail beckoned at the age of 81.
"From there I got the bug again and had to keep cycling," says the great-grandfather of seven who has three children.
Karen, 66, lives in Taradale and Mark, 58, is in Te Awanga.
He again casts his mind back to when he was 16 and comes up with a former schoolmate, Gerald Ogg, now a psychologist in Auckland, with whom he rode a home-made tandem bike to Auckland and back.
Only last December, another teenage cycling buddy, Derek Rixon, died. They did the Wellington-and-back trip.
His training in the past few months has been going well with two 60km rides a week with just as many 40km ones.
"I do feel very fit and healthy," he says, happy to drink lots of water and eat intelligently while warding off "sweet stuff".
However, McGavock is mindful anything could happen on the road.
"I could get run over or I could just die," says the man who attended the defunct co-ed Hastings High School before assuming the mantle of first XV captain of the school rugby team.
His father had sold the grocery store in Myross Bush when he was 12, transferring to Auckland as a Colonial Mutual Life Insurance employee.
Two years later the McGavock family moved down to Hastings when his father gained a transfer as Colonial Mutual branch manager.
"I'm only a newcomer. I've been here for 75 years," says the Bowls Heretaunga patron who spent this week competing in a tournament in Wairoa.
