66 Dart, 408 runs hot. HELP PLEASE!

Alright, I'm about at my wit's end with this thing.
Here's the details:
Initial build: 66 dart, MRL 408, ripped off 532 HP and 544ft lbs on the dyno. 11:1 static compression. Aluminum heads. Standard 8 vane Mopar water pump NON shrouded impeller. New Northern radiator PN 205152 26" core, 2 rows of 1" tubes. Spal 10" fans with northern radiator matching shroud. 803 CFM each. 35 degrees timing all in, 91 non ethanol fuel. Standard stant 180 degree thermostat with 2, 3/16" holes drilled in it. Standard bypass hose IS in place. TTI ceramic coated headers AND thermal interior barrier. Stock fender wells (uncut) stock valance in place.

Problem: runs like a scalded dog, but ALWAYS runs at 200-215. never crapped coolant on the ground, doesnt seem to ping (that I can hear). I run Schaeffer's 10W-30 for what it's worth.

What I tried to help the situation, in order.

New flowkooler water pump AND 180* Robert Shaw thermostat with Mopar performance silicone bypass hose. No change.

Cut off the dimples on the shroud and installed rubber flaps. No change.

Chooched down the timing to 32*, no change.

Pulled plugs, changed from champions to NGKs - they looked fantastic color wise and the color change on the ground electrode was dead nuts center on the bend, indicating the timing and flame front/kernel is where it needs to be. No change

Header tube temps are consistent. Within 10-15 degrees variation. 310-325 degrees after a spirited drive. They are NOT wrapped, nor will they ever be.

Chopped a hole in the hood - no change. (I'm installing a scoop later anyway)

The lower hose is NOT collapsing. I confirmed with a go-pro under the hood while driving.

I'm running a stant 16 psi cap with a 2 quart overflow tank.

This friggin thing runs at 200-220 (220 is below 25mph putting around) all the time, putting through town, romping down the highway at 90+, doesn't change much. Might see the occasional 190* but as soon as I drop to cruising speed, boom! 200-210. If I let it sit and idle for 15+ minutes, hood open or closed, it absolutely will not budge below 200-205. Ambient air temp doesn't change either. 50 degree evening or an 80+ degree afternoon, doesn't matter. Radiator fins are clean and clear. Id eat off of em, seriously. I've sealed off the radiator core to core support, and hood to core support, no change.

I know I'm going to get the "install a mechanical fan and be done" lecture. Not going to happen. I have 2.25" from water pump to radiator face. There's simply no room. Period.

I've confirmed my OE and VDO mechanical gauge readings with a thermal temp gun. Stat is 200-205 at idle. heads are 215-220.

So, any of you have any ideas? I'm at a complete loss over this thing. I've read numerous forums in general where people claim 210 isn't a death note, but for me, it just seems too damn hot.

Thanks a million.