The lighter the oil, the less power required to pump it, and the more quickly it gets everywhere it needs to go. I've been running 10W30 in the racecar for years, and I heat it before every cold start I can, using a Moroso pan heater pad. Zero problems. Roller cam, but I still add a little GM additive for the sake of the other valvetrain parts. The car sees 8,000RPM.
On my flat tappet cars, I've been adding 1/2 container of the GM additive when changing oil.