More coolant, less water, a full bottle of water wetter/motor max/royal purple , top it all the way off.
Also, again keep in mind when you are not moving there is no real airflow going through the radiator (the fan does not pull enough through it, really) to create enough evaporative properties to sufficiently cool your BB. I'd question the size of the radiator and the volume of the water pump you have installed.
Bill S.
PS: Last week I had ERA188 out on RT76 in Philly, stop and go traffic, 89 degrees, the
oil temp never rose past 180 degrees, the water temperature would sometimes go up to 210.......Another friend had his car top 240 degrees in the same traffic, differences in car (I have a 427BB he has a 427sb stroker) are really the radiator and the water pump capacity......Ambient air temps were the same, humidity the same, not the same time in stop and go traffic, but still the same type of stop and go traffic.......
PSS: Try backing off five car lengths from the vehicles in front of you and allow crisp clean flowing air to make it through your radiator and engine compartment..................