I have a max wedge 505 in my '64 Plymouth Savoy street car, also using an original 22 inch mopar brass/copper radiator, recored with a copper high efficiency 3 core. Using a high flow 440 source water pump (I know some don't like this pump, but works well for me), original aluminum '65 race hemi water pump housing, race hemi 7 blade aluminum fan with Hayden 2947 heavy duty clutch, and original steel shroud, all mechanical, no electric fans. I swapped from a 180 degree, to a 160 degree high flow milodon thermometer, which helps the engine stay cool, as the thermostat opens and lets the much lower temp coolant from the radiator do its job, before the engine goes in to thermal meltdown mode. In my experience, once the engine hits 180 degrees using at 180 thermostat, it is tough to get it the temps below 190 in the summer. Tip, a thin layer of Hylomar blue on the thermostat gaskets and radiator hose ends do miracles for keeping it sealed up. To aid cooling, you could increase the percentage of water in your coolant mix, such as 30% coolant/70% distilled water, or 100% water with water wetter added. I prefer using Zerex G-05 coolant 50/50 mix with distilled water for rust protection.
You could also try flushing your engine cooling system with Evalorust thermocure, even though it is a new build. I would not count on all the rust being removed from the coolant passages of your vintage block. I used this, and was surprised at the amount of crap that came out, new engine build also. It did help cool it a few more degrees by removing some rust from the iron engine block. Easy to do this on a weekend.
A quick experiment you could try, is run some 110 octane leaded race fuel. With no other changes, I added 110 octane leaded race fuel vs. straight 100 octane no lead race fuel, and my engine dropped immediately 15 degrees in temp. This was back to back, filling up at the pump. I usually now mix half and half 110 leaded race fuel, with 88 octane non-ethanol pump gas, which makes 99 octane leaded fuel. Saves a few bucks for gas, and I can get away with 34 degrees total timing, no detonation, and runs cooler. Your 505 will love the 110 leaded race fuel anyway, bump the total timing to 35-36 degrees and hold on!
One other quick help, remove the bottom splash shield behind the front bumper and in front the bottom section of the radiator, it helps to get more air flow into the radiator from below, and will cool your engine few more degrees. Hope any of these ideas help, as they seem to work for keeping my 620 HP 505 cool in the hot Utah summers. Mine stays around 180 degrees in the hot weather, but I have to keep the car moving a decent speed. If I stop at a bunch of stoplights, the temps start climbing to 190-200.
Looking to be over 100 degrees at my home today, so honestly, I don't push my luck with a 620 HP stroker big block mopar on a day like today. I try to wait to drive it until it cools down a bit in the evenings or morning, for fun blasting around.
Here are some links:
https://www.forbbodiesonly.com/moparforum/threads/hayden-fan-clutch-low-profile.115490/https://www.summitracing.com/parts/hda-2947https://www.summitracing.com/parts/mil-16405/overview/https://www.walmart.com/ip/Thermocure-by...9ffb0f66128fa6bhttps://www.walmart.com/ip/ZEREX-Antifreeze-Coolant-1-gal-Concentrated-ZXG051/119274583
