Hi Sean
You might try Herb Becker in Kitchener, Ontario. He's a retired machinist. For the last fifteen or twenty years he has been building racing Commando engines, land speed racers etc.
He definitely knows what to do with your valve guides. I'm not sure if he is taking work on, but if not, he could probably recommend someone who can. Ontario has a strong vintage Bike community.
The other call you could make is to Mike Partridge , owner of Walridge Parts in Ontario.
In Woodstock Ontario, Bruce Chessell operates Triton Machining. He's well known for Amal carb resleeving but also does full motorcycle engine machining and rebuilding.
He recently notified the Norton site the he was back at work after several years off. ( His wife passed)
bchessell132@gmail.com
Glen