The picture of the Craftsman at the bottom of this page makes clear the contrast between 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