There are fittings on each side of the lower housing similar to the GMC housing. So instead of having a tee at the water pump on the outside as you have, it branches inside the housing in a sense, one going to the heater and the other going to the intake and then re-entering the block at the port you have the petcock if they choose that type of routing. I don't think there is a need for two parallel routes, seems redundant and adds unnecessary parts and plumbing, as long as the water pump pulley is spinning the water will flow as long as a deadhead isn't created, and in this case it has an in and out just as yours is routed through the intake. The factory heater hoses don't go across the top of the valve cover, so there wont be a need to route them that way.
