What is the history of your truck? Did the truck motor cool OK before this or is this the first run up after installing the 235? There are two things not mentioned here that can affect the cooling. One is that the fan is not centered on the rad and therefore is not pulling air across enough of the rad. That is one of the reasons for using an old style water pump and an adapter plate. The other is the pulley size on the water pump. If there is not enough flow through the pump at idle it can be a factor. With some of these sixes, running at idle can be more of a cooling challenge than running down the road. From your description of the rad hoses, I doubt that your thermostat was the problem. However a new one could prevent a disaster sometime in the future.
