If it is truly a 1958-62 block it will not have a tube under the side cover. 1958 was the first year the oil supply is from a cast in galley up the center from the lifter galley.
1958 had a 1/16" orifice in the block that can get clogged, 1959-62 has a 11/32" orifice which would be hard to clog.
