My '57 with a 283 has trouble getting up to 180 degrees, I know it is not apples to apples since we're talking about two different engines but that is of little significance. My truck is very close to stock and I have an aftermarket temp gauge along with the factory gauge. I have tried several 180 thermostats with no improvement, a cardboard winter front in front of the radiator with different air adjustments can raise the temperature as high as I want to go but it is pretty hard to regulate it. My next experiment will be a 190 stat. I have an expansion bottle plumbed to the radiator overflow nipple and it works perfectly in keeping the cooling system totally full, my truck never had an exhaust heat riser flap from the factory and when I fabricated all new exhaust I did not include one.

1957 Chevrolet 5700 LCF 283 SM420 2 speed rear, 1955 IH 300U T/A, 1978 Corvette 350 auto, 1978 Yamaha DT175, 1999 Harley Davidson Softail Fat Boy