Mystery parts, Big Block or 6 cyl?
 

I have been digging in my bolt pile, gathering/organizing bolts for my two SB builds and found these. I have never had a BB or 6 cyl, so I am not sure how I got them, but they do not look familiar to me. Thx for any help!

ps, I know the valve cover spreaders on pic top are SB, but not sure about the lower ones.

Fairly sure they are used on big block Chevys

Yep, BB hold downs.

Check that long threaded alternator bolt for a "W" stamped on the head end (short thicker thread side of the hex).

Thx, no W stamped, but has an X or cross stamped in the end.