If your radiators are like sooo many of them I have had experience with, they are about half full of rusty scale and sediment. You probably noticed they weigh tons, it is because of the sediment.
We don't see many steam installations anymore, they are just too unhandy and subject to explosion. A recycler may be your best bet.
But, hey, if someone wants them to add onto a system or for a new systme; I have nothing against you or the buyer. I wish you the best.