Battling overheating new 360 build

Having a similar problem with my car was wondering if this ever happened to anyone and if it did what steps can I take to diagnose this so I also have a recently rebuilt 360 in a 69 Dodge Dart isles fine but for some reason can’t seem to stop overheating I thought it was the thermostat so I decided to take the thermostat off since I’m probably only using the car for the summer anyway but even with that it still manages to over heat when I start revving the car to 2000 rpms or when I start driving