The long brackets were made as a bit of an interim, some say for the special forces, to evaluate other telescopes. The Leatherwood was one of them. S&B were another but..... anyway! But by then the L42 had had its day and in any case, at the time the replacement trials were well under way resulting in the adoption of the L96 in '84/85
If you want to know what the L96 S&B scope mount looks like, it's clearly shown on the thread, in the CES.