Hi Mike
Some info about this engine:
It was sold to me and installed by Tom at TJ Mechanical  in August of 2017.  During the install, a brand new ACT clutch (pn 4200105) was installed and the lightweight flywheel was swapped over from my old engine.   
I took my Miata with this engine to the following conference race weekend and unfortunately, the head gasket let go.  So, I did the subsequent repair myself to prep the car for the October CACC#6.  This included removal and scrapping the head, to be replaced by a remanufactured head, a new timing belt (as the old one was covered with oil from a cam seal leak) and all new gaskets.   The new head has been shaved roughly 0.035” and should deliver a compression ratio that is a bit higher than stock. 
Before the new head was put on, the piston tops were thoroughly cleaned.   Careful lubrication procedures were followed to flush the oil passages and the engine was finally filled with Mobil1 10W-30 when completed.  Note that this engine has the long nose crank typical of 1992 and beyond 1.6L Miata engines. 
This engine with new head was raced for one weekend in October of 2017 and performed very well, with no problems.  Then I sold the car.