I don't know about the business today, but back when I was involved more heavily in such things Camshaft Machine Company./CMC and Engine Power Components/EPC both in West Michigan
used to make the majority of flat tappet cores for domestic brands and other cam companies....not just Purple Shafts, and they both also did quite a bit of cam grinding
for many different sources and brands. If you've ever noticed "CWC" cast into a cam, that is camshaft machine's tooling.
Lacking resources, for years I assumed it meant "chrysler windsor canada" and was told later on that was incorrect.

Knowing the way the industry is headed, it wouldn't surprise me if those are the next companies on some big ugly conglamerate's buy-up list.
Already happened to crane, comp, edelbrock, etc etc.