Some other items were, I believe, unique to the Lightweights. These include:- location of fuel filler and fuel tank, two rather than three wipers, steering column, no lip on wheel arches and exact location of roll bar ( uprights inside cockpit not boot). These are things that could not be changed ( though SB7020 was part built with a side filler and floor tank). Based on my own experience of having a car built AC were able to modify:- bumper mounts, dash, pedals, instruments, heater controls, door cards, headrests headrests ( deleted) and side marker on a non Lightweight MkIV ( or Superblower in my case). Lightweights were also fitted with 15, not 16 inch wheels - but that is very easy to do at any stage.