If it was me I'd contact Tim McMaster. Don't know where you are located but he is near Fresno, CA. He pretty much knows all things Y block. I'm sure there are other sources as well.
Unless it's for the supercharged / high perf engines, or the: 1.43 vs 1.54 rocker arms, locknut vs self-locking adjusting screws and improved push-rods...
original 292 and 312 valve-train parts are effectively the same.
You might be more specific on what you are looking for...