I am not up to speed on the motor mount options for a 460, but you may want to consider something like Total Performance or some of the other companies on Ebay that make a mount that is like a big eyelet/shock mount. One of the things I have always disliked about most Ford mounts is that they don't have a good fail safe catch unless you through-bolt them.
BTW, awesome engine, I am jealous, I am just too cheap to spend the cash on a Boss 9 stroker, but it would be so right in mine
I can't complain about the 489 FE though, been together for 12 years and hasn't missed a beat