Slick mag harness parts

[Flying Scotsman]

So here's what is probably a silly question...I started routing the mag wires today (Slick mags, the stock Van's/Lycoming IO-360). I pulled out the installation schematic, and...

I have BOM numbers that don't match the parts I have
I see part numbers that aren't on the BOM
There are parts on the BOM that aren't shown anywhere on the assemblies
I can't figure out what some of these dudes are for...

e.g., I've got "twisted brackets" that have a part number that isn't shown anywhere on the actual assembly diagrams; I've got two bolts that have a part number that also isn't shown; I see a part number on an assembly diagram, but I can't find it on the BOM on the same sheet at all...

Is this just a matter of "whatever...go make it work"? Or is the bag o' parts I have a sort of "stock" pick list of parts, and some of them aren't used? Or are they all used, but the diagram is ****-poor?

Anyone else with the stock Lycoming IO-360-M1B have any words of wisdom here?

TIA...

Steve