02 block vs 99 head question
 

I have a 99 Miata, my son blew out #4 piston@100 mph. Replacement 02 salvage block rebuilt and machined. 99 head rebuilt and machined. Which head gasket should I use? The 99 or the 02? One with coolant reroute ,one without. Called Mazda Corp and local dealer, no one knows. Any help would be appreciated!

Why didn't you use the 2002 head to match the 2002 block?

Does the 2002 have variable valve timing?

You may need to take the engine to a engine builder for inspection & advice.