Well, I have came to a stop on my engine rebuild, I'm trying to order a re-ring kit for my engine and I ran into this problem. When you go to order rings it lists metric sizes and 2 different standard sizes. I don't have any accurate way of measuring 1.5 mm or 3/16 of an inch. The oilpan on my engine is stamped 9-10-91 The pistons have a ford code of E7ZE-CA and the TRW stamp. I'm hoping someone here can tell me quickly what I need. (Engine is also casted F1SE BB by the driver side lower bellhousing bolt)