Overheating headache

Newer engine will run hotter

So many things to consider!

You say new radiator. Does this include pump, shroud, hoses and a High Flow T-stat, and the correct PSI cap for the radiator?

What is the base timing and the total timing curve?

All of this really maters and simply checking off the boxes sometimes hides minor things that get major.

Backing up the driveway should really not make it heat up. Heat soak and temp rise a little is normal.