By the time you buy a set of used rods, have them magged, checked for straightness, good bolts installed, and resized, you are almost to the cost of new rods.

New performance aftermarket rods are lighter, and stronger.

IF you are going to be buying custom pistons any way, you have an opportunity to use a smaller wrist pin and a longer rod (which allows a lighter piston) to save reciprocating weight, and even a 2.2 crank pin to permit the use of more available, cheaper chevy bearings.

IF you are going with stock pistons, of course, disregard the last paragraph.