Warranty 72 340 built

Lighter is better as long as you don't sacrifice strength. Basically, it will rev/accellerate faster. In some cases you can eliminate most or all of the external balance on cast crank 340's & 360's by using the right parts but it's not cheap. If you have a choice between lighter pistons or lighter rods, lighter pistons are the way to go. Weight reduction benefits will be better the further away you are from the crank. You don't want a lighter, weaker rod while keeping a heavier piston especially in higher performance & higher RPM applications.

SRP and Probe are some of the lightest off-the-shelf pistons.

Eagle & Scat I-beam are a good bit lighter than OEM rods but Scat are stronger because they are made from 4340 steel as opposed to the Eagle I-beam 5140.

Cheapest option in a mild application would be OEM 273 rods with good, aftermarket bolts. But the rods would still be over 50 years old and lighter pistons would be recommended IMO.