My 340 bare block

That block has a tube in the passenger side oil gallery. That means unless they drilled holes in the tube there is no oil to the lifters. If they plugged the feed to the drivers side gallery like they should have, there is no oil to the lifters on that side.

My best WAG is they drilled those holes to get some extra oil in the lifter valley in the hopes of getting more oil to the lifters.

I’d drill and tap them and plug them. You don’t need all that oil blowing around in the lifter valley. There is already plenty of oil there.

Just my best WAG.