I think any tire dealer worth his salt will advise against running any tire30-40 psi less than what it is designed for. This will increase the heat generated in the tire and thus make it more likely to fail on you. You may never have a problem but it would increase your risk. The manufacturer puts the tires on a vehicle with the specs. to match the vehicles capacities and abilities. This being said there is nothing wrong with increasing the load range on a tire. I myself have gone to d rated simply because I haul a camping trailer occasionally. I do feel that goin to an "e" is overkill and you wil notice it in your ride. "E" rated tires are what come on most 250's so I don't see the need for them on a 150 but it is your choice. Hoped my babel was some help!!