Not sure about those rattling plates , BUT I can tell you my experience w a Texas Car still in Texas , when I bought it 2 yrs ago it ran hot...usually 220-230F and crept up in uphills...The foirmer owner had re-placed the orig. 350 w a 400...he installed an elec. fan to try to keep it down...I found out it was missing the "X" fillers ( between radiator support and nose) ,also it was missing one of the masticated fillers , replacements now are rubber....I already had the filler underneath....then I removed the electruic fan that now was just restricting air...now it runs cool, yesyterday in 98F weather it ran 195F on freeway at 75-80 mph , got up to 200-205 F at 90 mph...at a VERY LONG redlight it crept up to 210F ,but back to 195 again driving 50 mph...
I think you got to
1) make sure you have all the fillers
2)make sure you have a thermostat, without one water will run too fast thru without getting cooled
3)make sure radiator is clean..no restrictions , and 4) possibly those rattling baffles have something to do with it too...