Mystery parts, Big Block or 6 cyl?

[KevinW]

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.

[RobR]

Fairly sure they are used on big block Chevys

[AnthonyS]

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).

[KevinW]

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