1970 442 is it OK to T the pcv valve hose off the power brake vac hose or will that take away vac from the brakes

 

I'd have some concern about oil vapor getting into the brake booster diaphram.

What's keeping you from routing the PCV vacuum line to the front of the carb?

 

While both are at manifold vacuum, I'd run separate ports the way the factory did. The PCV should go to the base of the carb. The booster can be fed from a fitting in one of the runners if there isn't a port on the back of the carb.