holley metering block ?s

I came across a pair of metering blocks that I don't have any info on.
Thought someone may know by looking at them who may have worked on
them or if they are a standard holley part.
They are marked primary and secondary on the top.
Pictures show #s stamped into the bottoms.
Google searched the #s and got nothing myself.
Got them in a lot purchase from a guy who knew nothing about them same
as I.
Anyone have any thoughts or care to make a guess.
They appear well done so I was thinking they may be professionally modified? But how to
determine what usage? I believe them to be from the holley HP line.
Any help would be great. Hope the pictures are clear enough to read.