I recently purchased a 90mm Angulon "kit" on eBay with all the necessary parts, including the focusing scales. One scale gets mounted on the moving track using a small strip of metal with a hole at each end to secure the mounting screws. (No problem here.) The other scale gets mounted using two very small screws (I think #1's) that screw into the bed.

My question is, what size holes need to be drilled in the bed for the mounting screws? And were they normally tapped, or were the screws just screwed into the holes like you'd screw a wood screw into a pilot hole?

I remember seeing that kit up for auction. Small world. I almost bought his other 90mm angulon, without the set up you got. Anyway....
On my Crown 45 the long scale is mounted to the keeper that holds the focus track in place. And the holes appear to be threaded ,or tapped as you put it. That keeper is solid and for the screw to hold the the hole would need threads. Other wise you'd have to glue it down I guess.

The good book only calls them: Screw-special.
If they are not #1's then they are #0's. The holes in the rail guide are taped or threaded. Take the bed scale to a good hoby shop and find the size that just fills the hole in the scale and that they have a tap for, hardware stores will not have smaller than #2-56.

No instructions listed for where to mount them either. Close to the left front is most common.

I have a lot of NOS focusing scales. Is there a table somewhere that I can correlate these with various lenes?