As for fitting, the 460 will fit. As was mentioned you will have to fab up the mounts but the 460 is actually a little narrower than the 4.6. The major problem will be fitting the ZF tranny in the tunnel. The ZF is taller than the Mazda 5 speed and the shift tower will hit. That may create drive line angle problems. I don't know if you can lower the engine enough to keep the tranny in line. I would get out the tape measure.
.