I’ve only seen V-10 redline listed as 5200 RPM by one source and I’m not all that certain if that’s correct; although it sounds reasonable.
Ford 6.8L Triton V-10 Engine Specs
I rarely go much beyond 3,500 ~ 4,000 range because there is little to be gained, I’m usually not in a hurry, and the noise and vibration get to me anyway.
The inherent mass balance of a 90-degree V8 should be quite an improvement at higher RPMs.