I realize that I don’t need a spacer block for the rifle to safely function, but I’m going to use one anyway. This rifle will be passed down to my son and his sons, so it is getting everything available that is safety related. I can always take it out if I don’t like it. My question is, which one is preferable? I’ve ruled out plastic, have found Italian steel and modern aluminum. Were there ever any USGI steel spacers? If so, does anyone have a source? I see steel ones on several of the normal suppliers websites, just curious if they are all the same.