Here is a pair of custom puller tools that I recently designed and built for a customer. These are used to remove impellers from large centrifugal irrigation pumps.
I designed these to use commonly available hardware for all the wear parts. The central nut is a grade 8 coupling nut, and the jacking screw is 5/8-18 grade 8 threaded rod. The central nut is captured in a machined pocket between the side plates and rests against a thrust plate that spans the side plates and locks into a slot in either side.
The top plates saddle over the side plates to prevent the sides from spreading under a heavy load. The customer will be using two different threaded rods on the sides to attach to the pumps (1/2″-13 & 3/8″-16.) So I drilled the center hole at 1/2″ and made the counterbore to fit the 3/8″-16 flange nut so the plate will hold either size centered.