And that's probably simply a matter of economics. When manufacturers can no longer justify producing parts at low volume, they cease to do so. There have always been more competitors in PS running GM parts, so the demand remains steady. GM parts are always available - and less expensive. As a Mopar racer I know this all too well
Regarding Derek Kramer, does anyone know if he's switching brands, or switching to a different class? Doesn't appear to have an engine shortage from the pics here (but what do I know?):
https://www.racingjunk.com/Pro-Stoc...&page=2&categoryId=26&offset=13&from=category