Thermostat or radiator?

again, thanks and I am trying just about all of the recommendations!

 

I've had radiators so bad that the aluminum metal between the tubes was falling out and they still worked fine. The fluid goes into the top of the radiator and out the bottom so unless the rubber broke down into very tiny pieces it would be sitting on top of one of the cooling tubes and have almost no effect. If unsure you could pull the radiator, turn it upside down and spray your hose inside it. You could even spray water into the bottom outlet hole and see how fast the water comes out the top.

It's certainly not a bad idea to replace the radiator as you could have some build up inside the tubes. Not enough to cause a noticeable restriction but enough to reduce the heat transfer from the fluid to the aluminum tubes. However if the temp isn't getting into the red you should be safe. If you need to work it hard, say pulling a trailer keep a close eye on it.