The real worry is when skinflint who knows the forks are dubious so he only ever rode slow, or trailered the bike to shows to win lots of ribbons departs this earth and the bike gets old sold to some one who does not know and they grab a big handfull of brakes .
Even worse if it is on an organized and they take 1/2 dozen other bikes ridden by fairly frail older enthusiasts with them.
Jake Robbins Vintage Engineering is the man to ask.
He rebuild a WNG fork for me using original lugs, and it functions faultlessly.
He also makes complete Castle forks with new lugs /tubes.
Perhaps M20 owners who wish a new fork could team up and order a batch.
No, not cheap.