Bruce, Our Olds 455 boat engine conversions (70 - 75 blocks) were originally equipped with valve rotators. When we do rebuilds and head/lifter/cam changes we leave the rotators out and go to standard retainers. With hardened valve seats and decent roller tip rockers the rotators aren't necessary - more trouble than they're worth, and they add a significant amount of moving mass to the valve/spring assembly.
Automobile(s): 1977 Coupe (blue), 1977 Coupe (yellow), 1977 Coupe (green)
Re: Valve rotators
Provided your guides, stems, locks, rockers and retainers are in good condition, with no set wear ( a wear-in spot that starts a groove ) the valves should rotate or dance while in operation. You can witness this if you set your timing using a timing light with the valve covers off.