Connecting rods are not that complicated. If they are of different weights there are places they can be ground down to match balance them I believe. You'd need to match each end and overall weight I believe. i would leave this to a professional machinist though, because if reduced in the wrong place they could fail.

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.