Coolant bypass hose?

You have a mismatch in model year manifold and waterpump. Until 1969 the bypass hose fitting and water pump fitting was 1/2 NPT and in 1970 the bypass hose fittings manifold and water pump went to 3/4 NPT. I suspect your 318 intake manifold is from a 1969 and older, and your water pump is an aluminum 1970 style and newer.