I'm building a 6.0L to replace my tires 5.3l in my 2000 silverado. I picked up an lq4 from a pull-it-yourself junkyard which appears somebody had recently rebuilt as it had brand new heads, a Fresh coat of paint, spectacular looking bearings, and was really really clean inside. Of course I ripped it all apart anyway and put all new bearings in it again, as well as replace the dish Pistons with ceramic coated flat tops with Teflon coated skirts. This is still a gen 3 block, as the cam sensor is in the rear upper portion of the motor. I'm using a set of Gen 4 rods, because I wanted the bush pins instead of pressed. I had two sets of rods like this available. One set has the following numbers. 250, 3847 GNK, & 163 on the other side. The other rods came out of a 2006 Denali with a 6.0L. They also have GNK 3847 casting, but all 8 have a notch slightly off center, at the top of the big end. This was not something done by a machine shop this was something done by GM. I'm wondering if anybody knows specifically what these were for.. (not the rods, the cut grooves... Lol)
Thanks. Image Attached.

 

They are cast that way. It's Likely an oil relief of some sort.