Is there ventilation between the main webbing above the main bearing and below the bores in those iron or aluminum blocks?

I noticed the LS guys are running ventilation in there to get some breathing back and forth and keep from having high and low pressure areas in the crank case so I went to look at my blocks and noticed on the BGE block there is vents there already between the center bores at least but they are not on the 5.7 blocks. I don't have a 6.1 block here now and have never got to look that close at any of the non-production blocks. There could be some other changes unrelated to the material that are helping HP production also.

There are lots more things related to material that can alter HP between the blocks than just ring seal. Temp should be more uniform allowing more compression(don't sound like they took advantage of that here). Vibrations should be dampened better allowing more stable valve train dynamics.