I'm with admin, dont use second hand pistons and rods. UNLESS you have an accurate idea of their service life and use, and have them crack tested. Also the rod bolts should be replaced, as if they were installed correctly, they have had their stretch, and are past there peak strength. You need to inspect the little end bearing, and replace if necessary. For the pistons, you need a new ring pack, and depending on the design, a new set of spiral locks. The wrist pin needs to be inspected for wear and straightness, and check that it rotates freely in the piston. If not, replace the wrist pin and have the pin bore honed if needed. You need to factor in the price of rod bolts and a ring pack as to whether or not its worth it, along with lucky dip if any further processes need to be completed.
In my job a have seen 5 or 6 engines fail due to the use of second hand internals. The reasons have varied, from fake parts, carillo rods that had exceeded their service life and not replacing rod bolts.
Quality internals can be had for not much money these days (if you excuse the current exchange rate). Is it really worth the risk? A dodgey rod can quickly have you up for a new block.