Most aftermarket pistons and connecting rods come in match wieght sets, but thats not the issue here. Your changing from the stock hyperutectic cast pistions and powdered metal 5.7 rods to a forged piston and a 6 inch forged afetr market rod. The issue isn't that they match eachother its the counter balancing on the crank that needs to be addressed. Anytime you make a change in rotating mass you need to have the crank balanced for the new parts. Wieght has to be added or removed accordingly from the cranks counterwieghts in order to maintain a balanced assembly. For the extra $150-200 it cost for balancing its the smart thing to do.