The car hasn't been driven in years and it just got back on the road. It has a brand new radiator, new hoses(including internal spring on lower hose) and new fluid. I filled it up and started the car. After a while I checked the fluid and it was obvious that the fluid level was visually lower in the radiator. I assumed this meant that the t-stat had opened and let water flow into the block. I added fluid to top it off about 1 inch below the radiator neck.

After driving it around town for about 10 mins, I stopped at a gas station and the overflow hose was spitting fluid out onto the ground. Does this mean it was overheating or could it have just been overfilled?

Car seems to be running fine, but I am concerned about driving it and possibly having some damage due to overheating.

It is a '67 440.

If I take off the radiator cap when it is running and see the fluid flowing nicely does that mean everything is ok??