Chris,
If you have installed the front radiator, in addition to the rear one, make sure that the water flows in the following order.
into pump from output of front radiator ( at the bottom of the front radiator) via one of the pipes under the car.
through block thenout of the head
coming out of the head through the thermostat or restrictor plate
from restrictor to top tank of rear radiator (should be the highest point in the system)
through rear radiator to bottom hose outlet
from bottom hose outlet on rear radiator to input of the front radiator (at the top of the front radiator) via the other pipe under the car.
The diameter of the pipes/hoses going to the front radiator should be approx 25mm inside diameter. Larger is OK but not required.
The electric fan mounted on the rear radiator, does it have a shroud around it? This is VERY IMPORTANT, if not the fan will just suck air around the radiator rather than through it and the effectiveness will be reduced by over 50%.
If the engine RPM is 875, then the pump RPM is 430 RPM or so. You can change the pulley on the pump to a slightly smaller one and increase the output of the mechanical pump. Alternatively, set the idle RPM slightly higher to 1000 RPM.
Regarding temperatures. If the system has a pressure cap (14 lbs) and you are running 30% coolant (no more as it becomes inefficient at higher concentrations), then the actual boiling point of the fluid is probably closer to 112 degrees Celcius. Yes, with the cooling capacity you have now it should be possible to keep the coolant temperature below 100 degrees Celcius.
Hope this helps.
Paul Vanderheijden
www.scuderiatopolino.com