I removed the bottom from the drawers and replaced them with net.
To make an opening for the cab heater I removed the bottom drawer and only kept the "door" which I sawed a hole in and screwed in place.
At the top was a cutting board which I kept to regulate air flow.
Simple as that!
Now for the bucksaw. A few months ago I made one for my dads birthday. And it turned out so well so I made one for myself too.
The design is completely my own and if someone want the plans I can send them as PDF.