Bast*** "Machine Shops/Engine Rebuilders" !

The early small blocks came with a drilled lower bolt. Later on they went to leaving one lower bolt out and using a drip rail. Either will work when the engine is fresh and the oil stays clean. The drilled bolt can clog on high milers with sludgy oil deposits. That's not as likely to happen with the drip rail system. With today's better oils, either setup should work fine.