I tried a reduction in profanity for last year New Years resolution, by noon on January 2nd I had given up...
Just a data point, I have owned three SPF with 427SBF. I live in the asshole of the US, which is Houston. One issue I had on the cooling systems on the SPF's were the cooling systems were so incredible efficient that I could not get my
oil temperature above 160F with the
oil cooler blocked on any day when the temperature was below 65F!! The only way I could get my water temp up to 185F was to buy the cheapest thermostat on the market that had zero by-pass when closed. Any bypass around the thermostat and my engine temp would stay at 170F. Once I installed a 192F thermostat i would run about 185F water temp. Remember the thermostat opens at it rated temperature but does not fully close until 10 degrees below it rated temperature!! So 192F doesn't close until 182F. Even when it was 98F out those cars would run 190F and unless I sat at a light for more than 3 cycles the cooling fans would never kick on. In fact I disconnected one fan so only one fan would kick on.
Don't know what your problem is, but if you are confident there is not any air in your system, duplicate the SPF set-up with same size radiator and you shouldn't have a cooling issue. My water pumps were stock pumps, cheap thermostat housing (would warp easy if overthightend) stock pulleys. All Roush engines.
Not a fan of Roush engines but I am a fan of their resale value. I wish I had every SPF I ever sold as they are worth more today than when I sold them and I made a profit on every one of them ignoring my labor (which is some cases was a lot, lol).