Thanks for the ideas guys , It's a DW5 Jason it's from an ex BT Van it isnt the hot air type but a water one and deigned to plumb into the vehicles plumbing system to warm the engine up, it automatically turns of at set temp, but my idea is for it also to run an Auxillary heater inside of the truck as well, ideally want it out of the inside of the vehicle, little worried about carbon dioxide poisoning! Plus will be best under the bonnet, didn't think it would fit, but thanks to some above posts I now know it will