RustyBob might have a good point.
My engine is a small block 427, making well over 500hp. I use a standard Mustang replacement 2 core alum radiator, a 16" spal fan in a stock Mustang shroud, 180* high flow thermostat, and a mixture of 25% glycol and Water Wetter. Nothing fancy or special.
It'll get hot if i'm stuck on a lot of traffic on a hot day. We did the Cruise Colfax in Denver this year. We slowly moved west to east, all the way across denver on Colfax Ave. When we got to Aurora, we turned around and headed west. As we got half way back across town, we were stuck in traffic, light after light. Denver has no concept of traffic light synchronization. As we pulled in to the last stop, the engine was getting close to 220*. Not bad considering it took us more than 2 hours for the trip.
I track the car pretty regularly. Even when air temp runs about 100*, I don't have any trouble with engine heat; 20-25 minutes of high RPM use. Max water temp is right around 220*,
oil temps a touch higher. After the cool down lap, water temp is almost to 180* by the time I shut it off.
On a cool or cold day on the freeway, I have trouble getting it up to operating temps. I'v had to block off the radiater with duct tape to get above 160*.
My cooling system is nothing special, just off the shelf parts. The radiator isn't even tunneled in like yours is. Your system is much more efficient than mine.
I would check timing - base and advance - and get it on the dyno to check fuel mixture. Those two simple things can really make it heat up.