Anchor sells lots and lots of types of mounts, and Lord is another mount company. Look and see in both of their catalogs, should be able to find a mount to use without modification.
My Spicer 6041 was also mounted with rubber in 4 places. One mount is wide to resist torque, but still rubber at the ends. I can't link a picture right now but have a look in my signature in the 3-53T Detroit folder.
Also, have you measured height when installed? Looking at my 6000'series Spicer and my 51 GMC it pretty much has to be mounted just behind the cab so it can be high enough to not drag the ground. Under the cab close to the main trans Is where I wanted it but don't see how it would fit there.
