? about that 3.65” crank

Nice work detective! Let me ask you a question, what piston could I get/use for a 340 main, 3.45 stroke crank in a 340 block?

Is it SB Chevy rod pins? If so, they make a 6.200" rod that would work with 1.67" CH 360 pistons using a .927" pin or press fit with the small end modified for the .984" pin. The rods are cheap enough and longer than stock, so the benefits (geometry plus lighter .927" pin) might justify the cost of a custom piston or at least a modified (by the mfgr.) shelf piston (still cheaper than a full custom set).