the oil system has a main oil way, the rear balancer bearings simply have a take off from this.
the plug is where GM drilled the main oil way to supply oil to the rear balancer bearing.
one way to blank of the oil supply is to replace the bearings with a machined collet, this must be a force fit so that it does not fall out.
another way is to force the bearings 7.5mm further into the engine, this blocks off the supply
you could also block off the supply from the main oil way dunno..
