Lowest cost option might be to rebuild the head and replace the gaskets. The bottom end is pretty durable. In fact the bottom end on your truck is 99% identical to the 4G63 turbo found in VR4s and DSMs. A DOHC head will bolt on, but switching everything from East-West to North-South is trickier.

It might be as simple as dropping the head off at the machine shop and asking them to give it a check up. Maybe piston rings, too.