see the threaded holes in the bottom of the saddle - there's a plate bolts to that to stop the saddle lifting. I'd probably make a new part that allows for a tapered gib there as well.

For the actual gib I reckon there's enough material to machine the gib face to a taper and then put a tapered gibstrip with a slot in it to accomodate the adjuster which will fit into the end of the saddle.