The picture at the bottom of this page contrasts the more robust arrangements used on the Atlas version where the headstock casting was extended rearwards to carry the backgear, and the cover pivoted off ears at the very back of the assembly..
As a contrast here is the arrangement of the Atlas 10F bench-mount countershaft with the rear of the headstock casting extended to provide a mounting for the backgear shaft.
A publication containing full details of every Craftsman, Companion and Dunlap Metal and wood-turning lathes is available. E-mail for details. A manual for the 10 and 12-inch Craftsman metal-turning lathes is also available - Manuals Page