As a fifteen year old apprentice, some few years ago, I worked for a company that ran quite a few Traders. The thing that sticks out in mind about them was that a fitter and an apprentice, well versed, and with all the tools and engine lift ready, could change an engine in less that three hours. It became a bit of a party piece doing them. We use to keep a re-built engine on the back of the recovery wagon, and do them on the side of the road. They were a very easy lorry to work on.