Hot engine hard cranking. Need help to solve. Should I swap Aluminum Radiator for br?

1957 Studebaker PU 350 CI SBC has 3000 miles since new. Installed new cermachrome headers and 2.5 inch exhaust, new Duragold 1000amp Battery, New dual 1 inch tube aluminum radiator (Summit) New thermostat, new temp fan switch new high flow aluminum water pump, new 12 psi pressure cap, new coolant. Forced air 16 inch 7 amp fan in aluminum shroud. Nothing I have tried to get this thing to run below 220 degrees in stop and go traffic seams to work. On open hi-way at freeway speeds it is fine. I just want to crush this beast! Should I install a br radiator next?