Blazin' Bob, you didn't go to the ebay link. There you see the 992P is an Ertel part number for a 360. There were several piston manufacturers around back in the day: Ertel, Zollner, Nylen, Badger, Sealed Power, etc. Their part numbers were all over the map. Confusing at best.

One measures the piston diameter at the skirt about an inch up from the lowest point. If there was a manufacturer's catalog it'd say exactly where. If the OP has already measured 4.036 on the piston, the piston is most likely 0.040 over. The cast pistons with steel "autothermic" inserts were usually installed with 0.001" clearance.

R.