a little more - you should definitely have a 'stat because having no restriction at all in the flow will result in the engine overheating because the water will be flowing too fast to pick up enough heat and not staying in the rad long enough to cool well
the thermostat sets the minimum temperature, the maximum temp shouldn't be much above the rating if the system is a A-OK, running at 190 with a 180 stat isn't unreasonable, but with a 235 it should really be closer to 180, providing you're using an accurate gauge or thermometer - if so you might have a poor 180 stat, and certainly in your area you could be using a 160, but never trust an old truck temp gauge, check various points on the engine and rad with a non-contact laser thermometer
Bill
