I have a K series and carry loads of tools and spares. I have fabricated a box out of aluminium that is secured in front of the heater using rivnuts. I use a Tupperware type sandwich box with tools and spares that drops inside it. On top of that I put my spare clutch and throttle cables and on top of them I put my bag that contains a jack, wheel brace, tow rope etc. All secured by stout bungee straps. Pics to illustrate.