Well you said you need a new radiator. So that and the pump will fix all problems. I would put in the radiator first as it can be the main cause of overheating. If it can't get rid of the heat fast enough then there is a problem. Also if the pump can't pump the water through the system fast enough then that is a problem. So it's up to you and the money you have. I would do the two of them together and it will fix the hole problem.