I would make an adapter plate with slots milled/chiseled/filed roughly
the shape of the ways, rig up a way to clamp it in place level and
square to the ways, then oil the ways and fill the space between them
and the plate with metal-filled epoxy.

That won't do because there is no way to feed the work into the chucked
drill without loosening the clamp and losing rigidity. You either have to
mount a fixed workholder to the (movable) carriage, or have a motion
component on the workholder itself.