[ERA Chas]

El,
My So acts exactly as yours before your testing: T'stat opens at 180, temps while moving remain 180-190 (6000+ RPM) slowly inching up to 210+ standing still. I once saw 227 waiting at an accident scene a mile from my house. I'm lucky the brass tank held together. This has been the case for 17 years and I've lived with it and driven accordingly.
I have replaced the orig ERA copper/brass with their Griffen ally rad. (10 or so years ago) The most notable effect was that it heated slightly more slowly and cooled much more quickly. I have the EDE HV pump.
I realize now because of your thread, that my March pulleys are probably the cause of both our problems because the WP and crank are almost the same diameter. Actually the WP is larger than the crank. So it's not overdriven.
If I found that were the case I'd probably change the WP pulley, but again I don't parade the car and have no imminent need to do that. I also know Houston is generally much hotter than LI.
I think your biggest improvement (it's all relative) will be the pulley change and no shroud. (I never tried one)
Everything else suggested is either an incremental improvement or none at all.
We're all pulling for ya so keep up your fine work.