Hi my name is Ed I'm new to this form and Pontiacs however not new to other GM products, I recently purchased a 68 Firebird 350 350 2 Barrel fairly stock and honest car. since purchased I was concerned about the coolant level in the radiator fluctuating this may be normal just wanted some opinions.

with the vehicle running (idling) at temperature with the cap off the level will fluctuate from the filler neck to about 5 to 6 inches below the filler neck. At this condition there is approximately another three quarts of capacity that could be filled in the system.

Vehicle does not overheat in traffic or in the driveway when performing this test it operates at roughly 190° F I have replaced the thermostat and flushed the whole cooling system confirming that there are no blockages in the radiator, heater core or engine block.

When the radiator cap is on (16 lb) it will run and maintain the 190 ish temperature under all conditions.
My concern here is the radiators feel firmer than I would expect them to be The radiator hoses are firmer than I feel that they should be. You can squeeze them in approximately an inch to an inch and a half but you cannot pinch the two walls together.

Any feedback opinion suggestions other tests that I should try are very welcome thank you very much