Some updated info for any interested parties. The jet shop I used to work at has a material analysis gun, I replaced the springs/retainers in my heads, so they're sitting around and I asked my brother to bring a spring and retainer into work and scan them for me.
Gun has a bunch of materials stored, but will give the breakdown for things not in it's database. Retainers came back as 4140, all good. The spring....well, I need him to recheck it, as the breakdown seemed to indicate 01 tool steel. Not something that's used for springs in my experience, but neither is a material that would normally be check there, so neither was stored in the gun and it gave the breakdown instead.
