FP4NC will take either CAT 40 or BT 40 tooling.
To run CAT tooling you will likely need to remove one of the drive tangs on the spindle face or shorten one if it has not been done already.
The drive slots on CAT holders are not symmetrical, having one slot shallower than the other ...standard Deckel drive tangs are both the same length on the earlier machines, by the
issue of the "Flip" head machines believe Deckel only used one drive tang, so no mod. needed on those machines.
CAT holders accept 5/8-11 threaded pull studs...and yes they are unique to Deckel and Maho as well i believe.
If using BT tooling then you need the pull studs to be metric thread (M16 i believe)
Number of sources for pull studs both metric or imperial...
Cheers Ross