After reading my factory shop manual for the Olds 455, it appears that these restrictors for the cam bearings are really pretty useless.
The issue with Olds oiling is that too much oil gets pumped to the heads via the lifters- These restrictors only restrict the oil going to the cam bearings, not the lifters. These two functions take totally separate paths. How is restricting the oil to the cam bearings going to help with anything? The amount of oil going to the heads isn't affected so why starve the cam for no reason?
Unless someone has a compelling reason why I'd want to keep these in, my instinct is to yank them out and throw them away.