Pulling the engine for new freeze plugs

Both the Hi-Po and regular had floating piston pins. I have never heard that the rods were different, but verify. I have heard that the Hi-Po pistons are 2 types in a set - left bank or right bank. I hope you marked yours. Racers would sometimes swap them left to right to improve something. I assume true of the factory Hi-Po. I have seen a set of 4 after-market Badger Hi-Po pistons on e-bay described as "left bank".

I doubt the rods were cast. I have only heard of forged rods, even in later "make it cheaper" engines. I wonder if it is a crack. Forged metal it tough and usually necks down like Playdough a bit, not a sharp crack like brittle cast metal. Have a machine shop look at it.