How do you remove the pistons from the connecting rods??
There are gonna be snaprings, pull those out with snap-rig pliers and slide the wrist pin out.
every oem motor i have seen uses press fit wrist pins. to split em apart, you need a press and a specail jig so you dont damager anything. id advise you to take them to a machine shop, they will be able to do it for a reasonable price.