The old frame was removed from the body by one of the previous owners. He did this the wrong way by cutting open the bottom, right way is by cutting out the section between engine and passenger compartment and then lifting the frame out through the back. In this way the structure of the body is left in tact.Before he trew it away, the last owner made some pictures of the sorry state the chassis was in. He also toke some measurement of the front upper wishbone assembly since this differs from later models (federal and TC)and the S2 chassis is made to accomodate this, i.e. the upper trailing wishbone is behind the box instead of in it with the shock absorber.
As I decided to rebuild the car as an S1 I also needed to convert the chassis to S1 specs. This involved the adding of the boxes over the lower-rear wishbone. The plate which holds the pedal assembly is present in an S2 but the plate hangs lose to allow the body to fall over it. So for an S1 spec frame this is welded to the middle bar and the new boxes giving more strengh to the frame. The open ends of the front-boxed section was also reinforced. This is done by welding it shut leaving just enough room for the suspension. The top of boxed section is raised at the suspension opening to allow for suspention movement. This brought down to make it stiffer and later only the material that constraints suspension movement is cut away. Also holes for the pedal assembly are made. At the rear the fastning plates are removed and the fork is reinforced by welding plates in the open section.