There was a problem a while ago with the new water pumps coming out of the box with the impeller not located in the correct place causing the engines to run hot
Clovis had that issue with his 64
I do feel you pain about doing a water pump replacement job especially twice
Joe, your car is not flowing coolant through the radiator when sitting at a light. Could be a poor performing water pump or the engine could be running lean. A clogged radiator will overheat at road speeds, not your problem.
The water pump with the round style impeller is the better pump. Send it out to get rebuilt. I use the flying dutchman to rebuild my water pumps. Look him up on line.
If you go with a new store bought pump, check the clearance between the impeller and body. Should be around 1/16 or less, and be even all the way around.
Good thought Russ
Check your plug color if you think you could be running lean only after a complete tune up with all on spec
If lighter than a brown paper bag (color they SB ) your cylinders are burning lean and hotter than they SB
( disregard if you know that already )
Here in Oz, i use Penrite 10/10ths race car coolant in the Fleetwood.
It will pull the temps back by around 10 degrees and has no glycol in it. So no slippery stuff on drag race strips... hence, race coolant.
I buy a 1 litre bottle of concentrate for $20.00 and that makes 20 litres of very good coolant.
Our Fleetwood runs bang on the quarter mark of the gauge on the hottest days with the A/C on. I'm sure you could get it where you are. (Sort of a reddish colour)
Its Aussie made too, so ya know its gunna be good. :-)