I don't have the pistons here or anywhere close to measure. I emailed the people to see if they can see the W stamped on the piston or not. The sites lists it to fit an 87 and shows production dates of 04/87 to 08/87, so I'm pretty sure these are W pistons (produced in or past April of 87).
Well...if the block is the W series (hopefully it will be when I see it) then I can use Z32 forged rods on these. Is there any significant advantage to using the forged Z32 rods over the regular ol' Z31 rods? Weight diff. maybe?
You can look on the back of the engine behind the valve cover on the pass. side, there's a plate with a serial # on it...starting with VG30, if it has an A or B at the end, it's a non-modified motor, if it has a W, then it's the modified W series. Also you can find pics of the motor on the internet that show where extra water passages are. Also the bottom of the block has chamfered bolt holes for the oil pan bolts so liguid gaskets can be applied, whereas the non-W block is completeley flat.