[DavidNJ]

I've heard of aluminium rods on the street but have never seen them. Aluminum is subject to high cycle fatigue. I thought they were just a drag racing thing (low number of cycles in their service life.)

Without more knowledge, I would replace them. Rebalancing will probably be expensive, since lots of mallory will be needed because of the higher bobweight with the steel rods.

P.S.
Titanium rods would minimize the weight difference, however they would probably cost $4k.