Dave Martin in the UK has graciously shared his plans for a tool to safely remove and install the rear leaf springs on an Interceptor. The dimensions and other construction details are in this Microsoft Word document.
Frank asked, "I wonder, however, about the 20x20 mm cut-out in the vertical brace. Can you explain, to the ignorant, what this is?"
Dave answered, "The cut out is under the central hole in the top face. It is to allow for the length of the central spring location peg when it is in place. And to allow you to see that the peg is engaged."