From this...
To this...
You can see the work in progress below and the final version. I used the Gaslands 20mm Interceptor Driver available from North Star Miniatures as the driver, cutting the shotgun arm from the standing figure and swapping it with the seated figure. Added some plating for Chumbucket (yet to be painted) to stand on and a fuel can (which you can keep in the back of the vehicle in the game). I added some wheel spikes and used a piece of a toothpick to create a bar for Chumbucket to hold on to. I also added a ram bar and exhaust pipes to the vehicle, as well as the engine block and removed the windscreen.