It is my understanding the pcv can be connected to either the power brake or pcv port on the carb, since both are full manifold vacuum. They can not or should not be shared. So if you are not using the power brake booster - I do not see a reason on why you can not use the rear power brake port
Most of the power brake plumbing that I am familiar with connects the brake booster to the intake manifold and the PVC is normally connected to full manifold vacuum at the base plate of the carb.
