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

Thanks!
I thought that there are only 9" or 12" long arms, but I've just found that there is 10" arm (Jelco SA750E). I wonder whether there is a huge market for 10" arm if somehow it cannot be easily tweaked to work on a plinth where 9" arm was used.

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. ;-)

Many thanks.
I have a plinth that has a hole drilled for 9" arm and I was wondering whether I could fit 750EB, but I guess not without drilling another hole.
Good to know that 10" arm is not uncommon.