This is from a burned out memory, lol.
Got my 1st car(68FB 350 HO - w/o gauges) back in 75.
Had a factory clutch fan with shroud. Stock radiator. No baffles in front or top.
Drove-n-street raced it all summer no overheat prob.
Installed a 70 RAIII engine w/a TH350 trans next spring. Drove-n-raced all spring no prob.
But noticed it was so hot under the hood with both engines.
Installed a set of aftermarket gauges in July.
It was run'n 210.
So of course i put in a 180. Then it was about 195.
So...put in a 170. Now it was about 185.
It felt like it was slower, so my buddy run me in his 68 Roadrunner. We tested each other whenever one changed som'tn.
Sure enough, it had. So put the 180 back in and ran him again. It was back.
From then on i found all my HP Pontiac street engines like about 190 "at the line" best.