not in the service manual
A quote from "How to Hot Rod Small Block Mopar Engines book: "At the rear of the block near the #5 main, is the access holefor the vertical oil passage.It's drilled from the main cap parting area straight up to the rearof the right-hand oil galley.The trick here isn't the hole itself but the plug that is pushed in part way up. On a stressed relieved block, it has to be replaced. On any new engine build up, check to be sure it's installed. Without it, the engine ends up with very low oil pressure."
Still looking for a picture to show.. tmm