Most parts are no longer available.

Gaskets and bearings are no problem as they are shared with the blacktop.

Pistons and rods are no longer available.

You could do leak down test but bare minimum it should turn over.

I would do a deal where you can pull the head before you take it away. If the piston crowns look good along with the bores you take it.

If it needs a rebuild there are cheaper ways to do it but if the engine number is there it will always be an Rs engine and carry a premium. I wouldn't touch it with out an engine number.