I have read that Pontiac purposely designed the Firebird to run relatively hot (200 to 230) to promote complete combustion. I have a '68. Like you, I am looking for ways to allow the engine to run cooler. (my 2011 Camaro runs at 204, even when the outside temp is 95 degress) I have read that the high temps are not good for the head gaskets and don't want my coolant and oil mixing. I have found plenty of advice for 67 and 68s, but not sure if it applies to 69s. As an example, its recommended that the coolant be mixed 33% antifreeze/ 67% water. The water pump diverter plates require some adjustment to improve flow, but again, I think the 69 water pump may be different. Sorry I am not much help, other than to calm your concerns about running hot.