RT Heads

My brother has a pair of magnum rt heads from his 402 crate motor. they are complete with the factory rockers. Have less than 400 miles on them. He put a set of aluminum heads on the motor and is thinking of selling the rt heads. Anyone Know what they might be worth? I thought around 400.00$ for the pair. I'm not to sure so I thought I'd throw it out there and see what you think. They are not for sale yet. He just wants to get a idea what they are worth first. I'll post some pics later today. Thanks guys.