I have a set of pistons, not sure of the size, but the are too large for a b18a block i have. on top of the pistons the say P73. How can i tell what kind they are, i was told once that they are itr, but i would like to know for sure

 

P73 is the code for most ITR specific items such as the pistons, so yes, they are from an ITR. And they should fit the B18A1 block, both the LS blocks and the ITR block are bored from the factory to 81mm, it's possible that they are the factory overbore pistons, but not likely.

 

is there a different code btwn jdm itr pistons and usdm itr pistons? are both labelled p73?