Yellow rose, actually you can have too fast flow threw the radiator. A/C equiped cars had a water pump with fewer vanes on the impeller to slow the flow through the radiator for more temperature exchange to prevent overheating in traffic.
The rad cap has nothing to do with temperature as long as it is not letting coolant out.
I would be looking at the fan and fan speed. Is the fan an electric with the radiator? Those need a 40A relay and 8ga wires from the battery, through a 40A fuse, through the relay and to the fan. A temp switch rated at 190° in the bottom tank will control the relay. Remember it needs an equal ground for the fan.
If the fan is on the WP, does it have 5 plus blades and it should be centered front/back in the shroud.
You could also try the A/C WP.
