Thermostat recommendation.

yellow rose said
Google Stewart Components and call them. They have the size you need and make the best thermostat.

I doubt the air pocket deal.

Is the fan arrangement the same with the new radiator as it was with the old radiator.

I'll say it again...these old cars were never designed for electric fans and those shitty aluminum shrouds that do mostly nothing but block air.

Once you hit about 15-20 MPH the fan is in the way. If those electric fans and shroud are blocking air movement through the radiator, it will cause the engine temp to rise.

I agree w/ most all of these last posts , but in a lot of circumstances , it "is" beneficial to jack the front end of the car up when filling the engine and rad., I have even left them over night to let the air work out of them, especially if the top of the rad. is lower than the engine . <not many that way.
I have to raise my 68 fastback 440/505 to fill it -------------------