There was a guy (don't know if he's still alive) that was a specialist guru with Triumph motorcycles, real Triumphs, not the ones called Triumph today. I was dealing with him a lot around 25 years ago, I had a classic Triumph chopper, and in fact still have it today. I bought parts from him from an old school mail order catalog, and a primitive web site, and only once went to his shop to meet him. It was kind of a pilgrimage.
He did amazing engine work and rebuilds, and had an amazing stash of rare high performance parts. If you sent him an engine, he wouldn't tell you how much the work would cost, and he wouldn't tell you how long it would take. Lots of people got put off by that but that was fine as he always had more than enough work. Some people would get work done elsewhere, and then end up sending it to him anyway after someone else couldn't do it, screwed it up, or just didn't do it very well.