You would be addvised not to leave too large a hole that doesn't align with the hole in the bearing. It wiil have a tendency to try to hydraulic up the lower bearing and then squirt out between the block saddle and bearing. If the
oil isn't between the crank and bearing' it does nothing.There are more tricks like using a top bearing half that has a groove , cross drill the main journals on the crank so it is picking up pressurized
oil from either hole not waiting for the crank to rotate around again. Be sure to chamfer the hole openings in the crank in line wtih it's rotation. don't get carried away side to side. Your trying at this point to get as much
oil to the rod bearings. Replace any sheet metal plugs with screwed in pipe plugs. The plug behind the cam timing gear Top oil gallery should have a small hole to belch out any trapped air quickly and drool oil on the timing set.If your converting a pre 63 block to a later cam and bolt on cam retainer plate retainer be carefull not to block the oil to the lower distributor. We used to get a drill and gouge out the threads to one side of the bolt hole after a few first few threads to hole . So oil would run beside the 3/8" bolt. I saw a whole care off the ground trying to remove a distributor that had galled its't self inplace.