Over heating 66 Dart

I have a 1966 Dart GT with a 273 4bbl engine. The engine has been refreshed with new rings, bearing and gaskets. Original pistons were used since there was very little wear in the cylinders. I did change the cam from original to a Comp Cam XE262. The engine has the LD4B intake and a Competition Series Carter 625CFM carb. I put on a new water pump, hoses and a new aluminum 2 row radiator. The radiator is from ebay and it is one that looks just like the original in appearance. I don't know how good it is, but it fit with no modifications. New thermostat 180 degree. I have a five blade direct drive fan. It was an original fan from a 1970 Dodge Dart with a 318. The engine cools fine going down the road but when I sit in traffic for more than about 5 minutes the temp gauge begins to climb. It does not jump up fast, but gradually will begin to climb. Oh, I do not have a fan shroud. The car did not originally come with one, so I figured that it would not need one. The engine is not a super high performance engine. It is not that much stronger than stock. Oh, one more thing. I used 302 cast heads to have hardened seats. Heads are stock, but the ports were gasket matched. the intake was also gasket matched. That is all the work done to the heads. They were of course rebuilt with new valves, springs (Comp Cam), and valve guides and seals. The fan is about an inch and a half from the radiator. If anyone can give me any advice I would appreciate it. Thank's.