I agree its a bit archaic the catalogue hasnt even got page no’s and yes it looks like the good old telephone.

Buy or just make your own that could be done on the lathe it’s meant for. Scroll down for drawings that could be scaled up or down to then fit whatever lathe you have. https://www.model-engineer.co.uk/860/three-way-toolpost-by-david-lammas/

Minor thought…. Don’t use cast iron as that is a brittle material and could crack under high loadings. Do it in steel….. All commercially made tooling of this type is steel not iron….

All the best.

I would be wary of using cast iron for a toolpost, for fear of the tensile loads resulting from tightening the tool clamping screws.  Cast iron is strong in compression, but weak in tension.

With the upper part of the casting in tension, the sharp corner of the tool slot acting as a stress raiser, cracking might well result.

Steel would be my choice for a toolpost, for that reason.

If need be, make the toolpost by laminating three pieces of steel, clamped together by internal Allen screws.  That will  save a lot of milling and swarf!

That was what i did when I made my four way rear toolpost. Three screws for clamping, with the fourth location for a dowel to locate the post in one of the four reamed holes in the base.

Since your post will be three sided, use two screws, and use the “spare” location for a locating dowel.

Howard