i built this in the mid 80's, it went through many stages, there is another half van added in length,  four xj6 axles the rear axle has its crownwheel removed for less drag,  third axle drives, and both front steer , with two power steering racks and pumps,  racks were linked with an enclosed motorcycle chain.  never wore OUT tyre's. power was from a 5.2 dodge v8  auto... inside was fully kitted out with  hot+cold water on tap , shower ,toilet, fridge, cooker, grill, tv, and  double bed/ dining  area.  had  more pictures but the buyer borrowed them and  never brought them back,  i will load more if i find any...