PCM Ford/GM, INDMAR Ford/GM (Exception 1. PCM GT40 351 EFI uses Item #102506 located in circulation pump. 2. Not used 2007 up PCM. 3. Not for LT1 use Item #102506). Tapered threads are aprox. 7/8" in diameter. Nut is a 7/8" wrench size.
PCM 302, GT40 in circulation pump, Some Mercruiser (pt # 806490T), Early LT1 in the T-stat housing then moved to cylinder head around 95 (tapered threads are aprox. 3/4" in diameter). Also used in some PCM GM engines around 2002-05 located in the T-stat housing. 3/4" wrench size on nut.