67 Dart 383 high temperature question

If a engine is going to run at 210 or 220 degrees what thermostat you put in there wont make any difference. T'stat can open at 160, 180, 190, whatever, engine still runs the same 210, 220.
That 312 shroud number is brand new to me. I would like to see the details like bolt spacing, fan diameter, fan offset, just for comparison to the 67 LA shroud and 67 slant 6 shrouds I have. These 2 have the fan offset exactly opposite one another so the only different place the big block offset could go is centered.