Right okay. Well that's why I asked about the winter rating but the poster seemed to be concerned about high RPM (12-25K). I assumed that was when the oil was warm but maybe not
IIRC, guys with the HV/HP oil pumps were breaking them even when within the safe range for that 20W-xx Winter rating, and thus it wasn't overly relevant, lol.
But yeah, with a stock pump, much lower risk.
The engine never called for an xW-50, was always an xW-30 or xW-40 (Marine) from what I recall. It was never an engine that suffered from lubrication issues, so wasting pumping power on forcing molasses through it isn't doing it any favours; there's no appreciable benefit.
Also, I think he means 1,200 - 2,500RPM, there's no way you are spinning an SBF to 12,000RPM let alone 25,000, lol.