Tubal Cain described this in Simple Workshop Devices (WPS28). His aim was to avoid the shock of engaging a fine feed on the Super 7 only to find that threads were actually selected in the train to the gearbox. Here is my version of his idea which also takes into account the possibility of a non-standard tumbler stud gear having been installed for, eg, cutting a metric thread with the English gearbox:

I mainly use 33 and 34 teeth alternative stud gears so I have three double-sided laminated cards hanging on the little brass stud in the photo, the third for the standard setup with 24 teeth whether set for threads or feeds.

Steve:

For the use in mind, all you need is the extra tumbler stud gears, the point being that the expensive and time-consuming metric quadrant is not then needed. You might have to extend the arcuate slot in the standard quadrant slightly to accommodate the larger non-standard gears. The method has been covered extensively on the website complete with tables by other members showing the settings for the range of metric pitches available.

I posted this photo recently to show my arrangements for easing the installation process; you can see the non-standard 34T stud gear in position: