The GM Delco Gen 4 and the L87 rod (12641607) both appear to be cracked cap forged PM. If these part images are correct.The connecting rods are Powdered Metal/Sinter Forged.....Automotive manufactures haven't used Cast Iron Rods in decades.
GM has been using PM rods since the mid 90's so this isn't new technology.
Cannot even see a registration/parting line.
Should NOT be an issue. Wonder if rod bolt torque or bolt issue? That sounds improbable also given the wide range of years and units. Also robot torque checking and reporting QC systems in place
Leaves us with Oil pressure and MOFT.
The L87 doesn't look good compared to the Gen 4 rod right below if I had to pick one.
Yes, I have Tinius testing eyes

Gen 4
L87 (below)
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