If I run a vent hose from valley tray to oil tank do I need to run valve covers with crossover tubes?

Wouldn't have too, but either the oil tank or engine needs to be vented to atmosphere.Alot of moisture and alky will be evaporating off the oil at temperature.

Out of three engines I have, the only one with a hose between the tank and valley is the one with the crossover breathers. The other 2 have a gooseneck vent and an internally vented oil tank.

Peyton, is your oil tank internally vented?

Some horsepower gains have been seen in higher vacuum pressures from next generation oil pumps and only the dry sump tank is vented as the engine itself is running in a vacuum pressure condition.

I use a breather with a pop off valve. Peterson Fluid Systtems sells these # 08-1440 (-12 AN ) Closed system that breaths when needed.