Alright, first off are you going to be using this vehicle as a show car, or everyday driver? If it's going to be a show car, I say go with fiberglass. If it's going to be a daily driver, you need the bumper to be really durable and able to withstand any sort of conditions - urethane. Fiberglass is really easy to crack, bust, or break. Urethan is really strong and will withstand every driving as good as you OEM, or stock, bumper. As far as painting, you will have to paint the bumper before you put it on the car.
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