Time for a Compression Test and Leak down Test to make sure you're head gasket is okay.... then I'd be worried about the heads warping....

If the new Radiator hasn't helped it's time to check the water pump for proper operation.... Also possible that your system has too much "air" in it and needs to be burped.

Other than the Water Pump, Thermostat, Radiator, head gasket, and coolant lines/jackets inside the block and out there isn't anything else that can really cause over heating.

Also,

The reason you are going through O2 sensor so fast is because of that exhaust leak.

Fix that and replace with a new OEM sensor and you will be good as new my man.

Also make sure you are using HOAT certified/rated Antifreeze mixture (it's orange if I remember right)

 

"Time for a Compression Test and Leak down Test to make sure you're head gasket is okay.... then I'd be worried about the heads warping...."
This will get put on the list

If the new Radiator hasn't helped it's time to check the for proper operation.... Also possible that your system has too much "air" in it and needs to be burped.
Installed the new radiator and overflow last night. Had to fight to get temp up to halfway. Not a whole bunch of back washing out of overflow. Gonna make a test run tonight with the trailer on in 95 degree heat. So far, all seems good.
Other than the Water Pump, Thermostat, head gasket, and coolant lines/jackets inside the block and out there isn't anything else that can really cause over heating.

Also,

The reason you are going through O2 sensor so fast is because of that.
It's had a leak for a long time, just kinda got used to the noise and forgot about it. Could the over heating issues be helping with the O2 problems? Either way, the exhaust is on the list also.
Fix that and replace with a new OEM sensor and you will be good as new my man.

Also make sure you are using HOAT certified/rated mixture (it's orange if I remember right)
This is a new one. Is there any special brand?

Thanks everyone, all help and suggestions are greatly appreciated.

 

It's recommended to use the HOAT antifreeze from the dealer, but its pricey. I used Zerex G05 from auto parts store. It's basically the same thing, costs a little less. Make sure it is mixed 50/50 with distiller water. This is where you need to know your capacity of the system. For example, if you flush your system that holds 4 gals with distiller water, then drain it and only get 2 gals out, then you need to add 2 gals of UNdiluted antifreeze to it. This should fill it up and give you a 50/50 mix.

 

Just an update. It seems the radiator was the problem. Made a 45 minute test run pulling the trailer in 95 degree heat Thursday, all ws good. Did a 256 mile run yesterday, all ws good.

 

Awesome! Glad you found it. Thanks for the update.