Questions on a 72 Big Block Truck

My son just bought a very nice 72 GMC Camper Special C30 w/ factory air, tach, and big block. We are rebuilding the heater and A/C. There are 2 vacuum hoses that come out the firewall 1 goes to the vac actuator that controls the door under the hood then it then tees off and I think it is supposed to go to the heater valve that is missing from the inner fender. Is this right? The other vacuum line I think should go the the round vacuum ball that is missing from the side of the A/C box and then a hose from the vacuum ball to the intake. Am I on the right track on this? The other issue we have is the engine seems to run at the right temperature but after it is shut off and parked it pushes coolant out the overflow hose. We have put a new stat and cap and it does have the HD radiator. Should we install an overflow bottle or am I missing something that I should check first?