clean the piss out of it. then change all gaskets, but the heads. leave them on there.
rockauto sells a felpro lower conversion gasket kit, has the pan, rear cover, front cover, both crank seals, w/p gasket oil pick up and the oil filter housing gasket. for like 30 bucks.
re gasket the whole bottom end. and rockauto also sells the magnum lim gasket kit for like 40 bucks, comes with o rings and other gaskets.
then wire wheel all the rust off. clean it with brake cleaner and paint it up the color of your liking.