Unless you can find a set of really nice DO0E heads, or better, a set of GT40P's out of a 5.0 Explorer, you will be paying a LOT for a good rebuild and probably quickly exceed the price of a set of after market aluminum. Most of the OEM cast iron heads have badly worn valve guides and of course the valve are also worn so need replacement. And then a set of rocker arms because they are grooved, but then the studs are also bent or worn, so you need to pull them and install screw ins. Oh - and the springs have 100K miles on 'em so need replacement. The retainers and locks - oh he!!, might just as well replace them too. It's "only" a few bucks more. When you take a look, most of these heads are pre lead free gas so the seats are shot and need replacement. Oops - they are warped and need to be milled. A pair of $50 swap meet heads can quickly become a $1200++ drain to your wallet - unless you are really lucky