You can an engine rebuild with the block in the truck if no work needs to be done on the block. You will need to remove the front 3rd member(assuming still IFS), and drop the oil pan to be able to unbolt the piston rod bearing caps so you can remove the pistons.

I would go ahead and pull the head, then pick up/rent a micrometer/caliper to determine the shape of the cylinders. If the cyls. are within specs you could replace the rings(though cheaper to replace the entire piston), and reassemble it.

With only 200k, the block you should be fine for just replacing the gasket providing the PO serviced the engine on a regular basis.

If you do decide to rebuild the engine check enginebuilder.com for quality parts at damn good prices, most of us here buy from them.