Is the later 7.3 just a reworked 6.9 or are they completly different? Are the external block dimensions the same? When the time eventually does come to rebuild/replace the 6.9 I'm curious if a 7.3 will drop into the same mounts, bellhousing, clutch etc or am I asking for more grief here than it's worth? Thanks.

Don't hold me to it,but I am pretty sure they are the same block,just a little difference in bore and stroke.