I have converted several magazines. The converted magazines have the longer SMLE style forward feed lips and an SMLE follower.
I will try to find the thread and post a link.
EDIT
Could not find the post but here is a link to a related tutorial I did over on the CGN forum on Recteating the BSA Lee Speed Perch Belly Magazine.
https: //www.canadiangunnutz.com/forum/showthread.php/2002952-Recreating-the-BSA-Lee-Speed-Perch-Belly-Magazine?highlight=magazine