I'm now building all my wagons so that converting them just involves dropping the wheels out and swapping them over. My GER wagons are being built with S7 wheels to start with but my LSWR and LBSCR ones are convertible.
The shocvan is kit built and has small wires under the square blocks that the springs are over so that part goes up and down. The insulated van is a Dapol and that has a metal bar running under the one side that links the front and rear wheel blocks together. It is the same as the system on the brake van.
I have tried my brake van on the Warley Scale 7 layout and she ran fine which was a huge surprise and relief!