There is a frame available that bolts onto the chassis that can hold a bike rack/spare wheel/towbar, alternatively I have seen the spare mounted on the front but I'm a bit wary about that because it interups the airflow of the radiator. There is also a side locker that could hold a spare if the ZIG unit and caravan battery could be moved elsewhere.
Its one of the last Bedford CF2's with the 2 litre Opel 'high cam' engine, but suprisingly it only has the four speed gearbox with a high rear axle ratio, a reasonable speed until it meets any incline, one of the reasons I do not want to place the spare in front. I am looking into fitting a more powerful engine, there are a couple of vauxhall engines that are almost 'bolt in' but this of course would affect the insurance.
I want to retain dual capability, but thats given me an idea, fit the LPG tank in place of the spare, the existing calor gas bottle compartment which is adjacent to the locker with the battery becomes free leaving space for the spare tire. The weight I will have to check as I will be 70 in a couple of years but I'm pretty sure its within the 3500 KG limit.
Anyone who passed their test more than about 20 years ago should be able to drive vehicles up to 7500kg and 17 seats unless they are restricted for medical reasons. I have up until recently driven a 17 seater minibus and the only reason I no longer do so is that the people who loan the minibus impose an upper age limit of 65. Incidently the caravan is about 5 metres (16 feet) long and will just fit on my drive which is 5.5 metres long.