I gotta vortec 4.3 wanna swap with the newer ecotec pistons since they the same motors pretty much

They are not all the same. VTEC is made by Honda and has nothing to do with the other engines. ECOTEC and VORTEC made by GM are too different to interchange. If anything lines up or bolts together, your sensors would from that different engine would give readings to the main ECM that it can't compute. And also if the pistons are loose, throw that idea away and get pistons specifically for that engine. Throwing multiple separate engines parts together to make one functional one might work on older engines but since early to mid 90's parts are too picky to interchange between models and years.