Are Jelco SA-750D and SA-750E swappable?

I own a 9, 10.5 and a 12" from Jelco.. The 10.5, won’t fit on a Thoren 121 or 124. The bottom extend right in the middle of the edge of the chassis.

It won’t fit on the inside, and not long enough to anchor outside.
You have to anchor it to the plinth or in a separate pod...

Good arms though.

If you've never drilled an armboard hole before, it can be a daunting experience. But it's pretty easy once you get the measurements all correct. Let me know if you would want help

Thanks for your help.
My plinth already has two holes, for 9" arm and 12" arm. I don't think I would have another hole. ;-)