Is it an overdrive box as the title suggests?
If it's got the Laycock overdrive as used in 740s, my post here may be useful:
https://www.volvoforums.org.uk/showt...=M46+overdrive
Please note if it's not got the same overdrive unit it's unlikely to be the same seal, as I believe that overdrive unit has imperial specs rather than metric. If the numbers you've posted are the dimensions it's not the same.