I notice that several suppliers offer steel valve rocker arms as well as the alluminum ones....does anyone know if the steel ones were ever standard equipment ? I've had a couple of the newer alluminum ones have the pushrod "socket" get loose and they really make a loud racket, I would considder buying a set of steel ones to avoid the noise as well as the repair frequency, as always your thoughts are appreciated.

 

The normal noise maker is the push rod, that tends to wear down, become shorter and that will then make a constant lifter type noise.
As long as Rover has been building this engine, I believe they have used aluminum, GM may have use metal on the early engines back in the 60's.