I'm not much help, but if the rods are too big you can buy the 9.5 mm L-rods separately. For instance:

https://reverb.com/item/8777478-gibraltar-small-l-rod-ball-9-1-2-mm-sc-lbs

I would guess the rods pictured are 10.5 mm, but I'm definitely not certain about that.

Ludwigs of that era used a 3/8ths inch (9.5mm) L rod. I'd guess that 7/16ths is the next size up (10.5mm) and as such will not fit your brackets. As mentioned above you can swap out the ball arms to the correct size easily enough.

Your brackets, if original, are definitely 3/8ths inch, sometimes the outer holes will wear a bit from use and be slightly enlarged but the internal eyebolt will only accommodate the correct sized arm. Maybe the guy with the stand also mis-measured the arms on his stand. It can be somewhat difficult to measure these things with total precision unless you have the right tools. Ludwig has used both sizes through the years though so both 9.5 & 10.5 mm are possibilities on the stand.

Agree on the size... I remember they were same Dia as Slingerland leg mounts in '67.. we now know it as 9.5mm..

For what it's worth I have drilled out the case & the eyebolts in the past..from 9.5 to 10.5mm easy.

Cheers

John

If itn's not far away you could drive over there with a small tom to see if it fits.

It's about an hour. I'll just go with the smaller L arms if I pull the trigger on the stand.