Rotating assy balance

I doubt there is a gram of difference in each of those speed pro pistons hes got, but I could be wrong. To the OP, I would get a T gage and a micrometer, torque the rod caps to spec and then measure the big end hole diameters, and compare to factory specs for that engine with those rods. Do it with all the caps on the original rods, write down your measurements, then put them how your machinest said to put them and measure them again. Note the differences in diameters. Ultimately the onus is on you to make sure its all 100% correct on assembly including making sure ALL the oil passages in the block and crank are clean and blown out. Typically if the end user assembles it there is no guarantee or warranty. Had he assembled it, and it blew up, it would be his responsibility to make it right. Also ditto on the weld dingleberrys on the crankshaft.